I'm guessing other than polaroid, your only option is the Mamiya HM401 120/220 film back. B&H says they're discontinued, but you can pick them up for a song at the well-known Atlanta reseller.
Apparently there was a newer version that took 15 shots instead of 16 that supposedly had better film flatness, but I have no complaints. You get analog "exif" data or date info imprinted on the edges, and it needs a button cell to remember ISO when disconnected from camera. Also has a storage slot for the darkslide.
Hope that helps!