Based on the information provided I visited the Fujifilm page and found three products that are within the size range given. (3.25" X 4.25")

These are:

FP-100C Color ISO 100
FP-100B B/W ISO 100
FP-3000B B/W ISO 3000

I'll buy a pack of FP-100C just to try it.

Thank you all for the information provided.

Very helpful indeed.