I just picked up a Jupiter 8 and I decided to open it up and give it little cleaning. It has some fingerprints on the rear elements and some dust so I thought I'd have a go at it. It's pretty easy to disassemble but I lost one of the tiny set screws on the bottom ring (and it was already missing one). Any clue where i might find something like that? It's REALLY tiny. I was thinking I might pick up another one just for parts. Any suggestions?