I am interested in purchasing a prism finder for the Mamiya C330. They can sometimes be found on the auction site, but I can't afford them. If you have one in good shape that you rarely ever use, please allow me to make you an offer. I am not looking for the porro finder. I will try to add a picture for reference.
I've used mine a lot! And it isn't for sale I'm afraid
But for handheld use, I'd suggest using it in combination with one of the left hand trigger grips designed for the C330 and RB67s.
But it also works well on a tripod.