Diopters for Mamiya 645 1000s prism

I just got an unmetered prism for my Mamiya 645 1000s but need a -3 diopter as i don't like to shoot wearing glasses. Diopters for the newer Super/Pro/TL-prisms are widely available, but i couldn't find any -3 for the older ones.

I already checked Ebay, KEH, B&H etc. and sent an email to Mamiya Germany but didn't get a reply yet. Does someone know a source for the old correction lenses or if there are some diopters from other cameras which will fit?

Regards,
Matthias

Diopters from a Pentax Spotmatic/K body, Contax/Yashica RTS FR etc, Ricoh will fit. These use an eyecup to hold the round drop in diopter. Olympus OM round diopters should fit (but the Olympus eyecup will not).

I think early Canon & Minoltas use the same eyecup fitting.

I use the same +2 diopter in an eyecup on my M645 prism, Spotmatic SL, and Yashica FX-D cameras.

Thanks Tony! I will try to find one of those. If all else fails, i could ask my optician to grind one for me (which would have the added benefit of a possible correction for astigmatism).