While my answer to a past Atlantis question might not answer your present question entirely, you might benefit from reading it:
The reason why I link this answer is, in large part, because I think that you'll see that reading the relevant passages in Plato's Timaeus reveals that Plato doesn't have much, if anything, in mind beyond the immediate dramatic context (or there's no reason to think that he does, at any rate). This undermines the possibility that there's some connection to other stories.
I'll also add that there is no reason to think that Plato himself ever went to Egypt. The closest thing to a reliable biography of him that we have is from Aristotle's Metaphysics, and it doesn't mention Egypt. The spurious Seventh Letter contains a biography but it doesn't mention Egypt either.