Want to Buy Mamiya 6x9 roll film back

Looking to pick up one or two 6x9 mamiya roll film backs for the Universal Press/Polaroid 600se. Might even be into 6x7 for the right price but namely the aforementioned. Would prefer the version with the film memo on the back or one better with the shutter release accommodation. Help me get the GOOSE back on the LOOSE! thanks!