Let's just say I'm not aware of any evidence that he has, and this is a "dog not barking" that seems like it should be barking if Weiner's story is true.
There's a simple explanation for his behavior (from a poster on another board):
Simple explanation and the only explanation that is consistent with his behavior.
He's trying and failing to come up with an excuse that is both plausible and non-falsifiable. Unfortunately non-falsifiable also means non-verifiable. And while it might be plausible if he reported it to the police, asked Twitter to confirm his story and answered questions straightforwardly, it just isn't plausible when he won't even say that that's not him in the photo, and that it's "just a prank, ha ha" not worth wasting the police's time over, but worth hiring a lawyer and a private investigator to deal with.
Bottom line:
There are people who could back up his claim, if it were true.
But he has not apparently asked them to do so.