If you're talking about the old Polaroid sheet film holders (500 and 545), nothing has been made for them since Polaroid folded. Polaroid also made the 550 back, which used 4x5 pack film. Fuji made film for this holder up until recently, and you can still find the FP-100C45 film relatively easily. Finally, there is also a 405 back, which uses regular size FP-100C. This is pretty much your only option nowadays, as FP-100C is still being made.