There are other sources, but Darren gave you the easiest one. Aki-Asahi products are good.
__________________ "Payasam" means a sloppy pudding. Little kids love it, and I'm a little kid with a big grey beard and diabetes. Film: M6, M2, Ultron 35/1.7, M-Hexanon 50/2,Elmarit 90/2.8, Hektor 135/4.5, Canon 100/3.5, Jupiter 8 Digital: Olympus E-300, E-510 and E-3 with 4 Zuiko Digital lenses RFF gallery Flickr gallery
Unlike an M2 or M4 with a metal eyepiece, I find no problem with the M6 b/c the eyepiece ring is rubber. Is yours different?
I would also second Aki-Ashi having bought his for other viewfinders
David