Mamiya 645 Grips

[DevilDog4641]

So I’ve recently acquired a Mamiya 645, the original M645, and I seem to be having trouble finding the right power grip. Everything I find on eBay seems to be for the 1000s, Super, or something else, just not the M645. Any help pointing me in the right direction would be greatly appreciated.

I currently have the camera loaded with some Kodacolor II that expired in 1980. So I have the meter as low as it will go at ISO 25 and am going another 2 stops after that with the shutter speed.