I'm looking for arguments against the idea that you can have a priori knowledge of a priori knowledge. Perhaps appealing to an internalist account of knowledge and claiming that the justification for the claim 'I know X a priori' is not accessible to us?
I'm not exactly sure why the proposition 'I know X a priori' would not be accessible to yourself.
I know X a priori (by proving it without relying on empirical data).
Then I know that 'I know X a priori' without relying on empirical data
I would say that the transition from 1 to 2 is a matter of being aware that you know X a priori.
Once you know something, you know that you know it without having to perform experiments (a priori). You could go on ad infinitum.