I had an issue with mine that mysteriously subsided but before that happened, I was talking to arcadecup about repairing it and he said he could source a fly. He doesn't have them listed for sale though so the impression I got was that he keeps the source to himself for his repair jobs. So you might have a solution with him if you're willing to have him do the repair.
But if you do find a source, I'd love to buy one as well so please lmk!