For years now I have been using the Fuji FP100C45 in the appropriate Polaroid brand film pack back for testing in my studio.

I understand that one can also use the smaller FP100c film for this purpose in an appropriate back...my question is:

What instant film backs are/were available for this smaller pack film? Do they slide under the ground glass, or must they be attached via Graflok? My Polaroid pack back for the 4x5 material does slide in under the ground glass on my Sinar.

So, I guess I need advice and pointing to where I can obtain the smaller back.