For those of you reading this. I found my own answer by chance.
I found a 8.5x10.8cm Fuji MF Polaroid back.
This was key because it lets you expose the WHOLE sheet rather than a small square like the Hasselblad back does.

Basically used electrical tape to slap it on the back of the camera. Checked for light leaks and tried 2 shots, the second being perfect.

Now I can work on making the connection between the camera and the back a little more elegant.