I mean idealism, in that all is mind, as opposed to physicalism. I imagine that they would be more in the continental tradition than the anglo-american analytic tradition.
Freya Mathews (yes, spelled with one t) has been advocating a rather idealistic position as a "cosmological" version of panpsychism, but gaining little notice, certainly outside the limited panpsychic circle. Her most direct statement, I think, is ...
Panpsychism as Paradigm, in Michael Blamauer (ed), The Mental as Fundamental, Ontos Verlag, Frankfurt Heusenstamm, 2011. (http://www.freyamathews.net/downloads/PanpsychismParadigm.pdf)
Here is the introductory clip...
The gist of the argument is that a holistic or cosmological version of panpsychism, according to which the universe as a whole is the ultimate locus of mind, or of mind-like properties, can function as a rival to materialism, materialism being understood as the view which denies that mind, or any mind-like property, inheres in an essential way in matter or in other fundamental elements of physical reality. Moreover, I shall suggest that, in relation to materialism, cosmological panpsychism functions not merely as a rival theory but as a rival paradigm. I make this suggestion because materialism generates a number of intractable anomalies, anomalies that have become so entrenched in the philosophical tradition of the West as to seem inevitable. We perhaps forget that they are anomalies, and treat them instead as the very substance of metaphysics.
First, let's settle the terminology: Physicalism and idealism are in many respects opposite positions in philosophy of mind. But that doesn't entail that every non-physicalist position is a form of idealism. That is, there are a lot of non-physicalist positions that do not amount to idealism. Among these positions, the following were prominently defended and discussed in the 20th century: interactionist dualism, parallelism, epiphenomenalism, neutral monism.
Now, idealism is indeed not on that list. Still, there is recent work done by Robert Adams, who defends a sort of idealism ("mentalism") in phil. of mind, according to which
everything that is real in the last analysis is sufficiently spiritual in character to be aptly conceived on the model of our own minds, as experienced from the inside (35)
See his "Idealism Vindicated", in: D. Zimmerman and P. van Inwagen (eds) Persons: Human and Divine, OUP 2007, pp. 35-54.
Furthermore, there are some contemporary idealist philosophers in the broader sense (i.e. as a full-fledged philosophical position - idealism as in "German idealism"). Vittorio Hösle is a very well known contemporary idealist philosopher:
Vittorio Hösle (born June 25, 1960, in Milan, Italy) is a German philosopher. Having begun his academic career with extraordinary success, including the completion of his doctorate at age 21, he is the author of many distinguished works, including Hegels System (1987), Morals and Politics (1997, trans. 2004), and Der philosophische Dialog (2006). He advances an “objective idealist” theoretical philosophy, which attempts to revitalize Platonic and Hegelian thought, while also drawing from Karl-Otto Apel. His practical philosophy is a modified Kantianism, which also draws much from Hans Jonas.
How far back counts as contemporary? There are a few neo-Kantians left I'm sure, but they are usually more continental philosophy. If you are speaking of the last 100 years, there are quite a few. Third generation british idealists, like Muirhead, Colliridge, Collingwood and a few others. Harold Joachim made it till the 1930's. Italian idealism you have Beneditto Croce and Giovanni Gentile.
These guys were around after late Wittgenstein to around Quine's time so they are relatively contemporary. For those closer to the 21st century, you have Brand Blanshard who was active till the 80's very well into his 90 something birthday. The greatest idealist philosopher that's surely contemporary is Timothy Sprigge. He combines Bradley's absolute idealism with panpsychism to form a bizarre but impressive metaphysical system. If you are interested in another figure who provides many articles in favor of idealists' thesis but is more of a historian of philosopher, look up William Mander from Oxford.
Ignore the guys here who don't know what they are talking about. But notice that most of the guys I mentioned besides the Italian idealists in style resemble a lot more analytic philosophy than continental, you won't find Hegelian/Heideggerian ramble in here, or if you do it's far more mild. Also these guys are objective idealists, not subjective idealists or Kantians.
In "The Vindication of Absolute Idealism", Timothy Sprigge uses what strikes me as a quintessential analytical style of argument to establish what he calls "absolute idealism". Bravo! Brilliant. Tough to follow like most analytical "tedious arguments of insidious intent". Except Sprigge's argument ISN'T "insidious". But it's well worth the effort to parse it through. Quite a different approach than all the continental idealist philosophers from Kant onward and upward (and inward)....
Then there's quantum physicist Amit Goswami:
Naturally we project that the moon is always there in space-time, even when we are not looking. Quantum physics says no. When we are not looking, the moon’s possibility wave spreads, albeit by a minuscule amount. When we look, the wave collapses instantly; thus the wave could not be in space-time. It makes more sense to adapt an idealist metaphysic assumption: There is no object in space-time without a conscious subject looking at it.
And David Bohm
I explore the philosophical dimensions of Bohm's views in which realist and idealist, monist and dualist, contingent and determinist outlooks occur in creative tension. https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1467-9744.1985.tb00588.x
None. Even Continental philosophers will not assist you in that venture. They would likely say that to assert that the objects of thought are all that is real is too absolute, too exclusionary, possibly a tool of social order to devalue meaning, and thus wrong. Not to mention that as objects of thought, they're still just objects.
When Sam Johnson refuted Berkely's idealism "thus", and kicked a rock, that settled the argument for a great many people. "All things are thoughts" is too short a road to solipsism for anyone to take seriously. To avoid the solipsistic conclusion you'd have to take either Berkeley's own standpoint that God's experience makes up for the difference in experiencing the world's furniture, or be a radical panpsychist of a kind which I don't believe exists. Even Chalmers and his conscious thermometers still acknowledge that physical properties exist.
Sometimes there's no middle ground- idealism is a ridiculous notion without positing a large number of very messy metaphysical rules, all hell-bent on propping up the notion and with no other reason to be presented.
That all said, there's plenty of people who argue for a remnant of idealist thought- namely that reality begins with perception and not the other way 'round. I'd argue that's not really idealism though, as any such description still allows for an external reality to exist independently of the observer.
See this other question for more information. Apologies for the sloppy answer, but hopefully this'll attract a better one.
Bernardo Kastrup is a contemporary idealist. He might even be an ideal monist.