I need a replacement as my lens is totally engulfed with fungus. Can anybody direct me to any online stores that sell this or the 55mm lens, other than KEH and ebay?
You're best bet is to subscribe & place a wanted advert here In recent weeks complete 645's have been sold very cheaply & a spare body never goes amiss.
All Mamiya 645 manual focus lenses will work with your camera. You can check B&H photo in New York to see what they might have new or used, pretty sure they will ship to you. Also consider ordering directly from Japan.
There is an E**y store called shueido I believe out of Hong Kong that was selling as of last week a BNIB 80 MM MAMIYA lens for $ 119.00 plus shipping that to Mex. ( PROBABLY LESS TO AUS.) was $ 30.00. I don't see how you could go wrong with that. I bought something from them in the past having found them reliable and honest. Cheers.