I did not find other reading apart from "Open society and its enemies", but it's difficult for me to believe that Popper was the first and the last one who paid attention to this phenomenon. Popper mentions Kant and Schopenhauer as philosophers who were displeased by the appearance of this fashion in Germany (and Plato, Aristotle, Hegel and Marx as those who inluenced the developement of this style), but that seems to be all. I believe there must be other works on this topic with analysis of the origins and developement of Oracular philosophy, comparison of its representatives, etc. For example, did anybody call Heidegger a representative of Oraclular philosophy? Can anybody cast light on this question?
I don't have a copy of Open Society on hand, but from memory, I'm pretty sure Popper uses "oracular philosophy" as a term of abuse for a style of philosophy he opposes. Consequently, you're not going to find a literature using that term. The form of your question is then—through no fault of your own—a little like asking Is there a literature on Uncreative Philosophy or Unreasonable Philosophy? It depends on who's calling what uncreative/unreasonable, and for what reason, as nobody calls themselves that.
I think what you're after would therefore be more philosophy that is critical of certain philosophical methods in which philosophers (are thought by others to) offer indefensible wise-sounding claims. Rudolf Carnap's essay condemning Heidegger is a classic in this genre, as is A.J. Ayer's Language, Truth, and Logic. However, while aspects of their arguments may be right, the standards Carnap and Ayer hold a philosopher like Heidegger to are generally considered implausible standards, because they reject much that's of widely considered to be of value. Harry Frankfurt's recent "On Bullshi*" is a more recent contribution to the genre.
What this question comes down to, then, is (1) what counts as a meaningful assertion, and (2) what counts as a plausible argument for one. Those are the things I think Popper is accusing the "oracular philosophers" of missing. Those are two partly separate philosophical literatures, and they are each absolutely massive.