Just edited my post to be clearer about the distinction in formats/holders.
Florian Kaps is offering a limited run of sort-of-pack film based on left-over material from the Polaroid 20x24 project. But the price per sheet is very high - currently €28 for 3 sheets, €163 for 18 sheets:
And it's not clear whether he will have any follow-up when the 20x24 material runs out.
ADDED: I wrote "sort-of-pack film" because they are unable to replicate the original film packs and instead are offering the film in individual-sheet boxes that fit the pack film holders.
I just bought a Horseman Polaroid back for my Horseman VH-R. Near mint condition with the rangefinder compensation adapter. I have a lot of pack film, so I need to expose it all before it expires. After the pods dry out it is useless.
Once I expose all my Fuji 100, I'll probably put instax film in there with a pull sheet to get it through the rollers. One exposure only , however.
I have the Polaroid back for my ETRSi and I have several FP-100 in the fridge - I don't use it regulary but I'll keep it.
Everyone who is interested in the Bronica ETRS Polaroid back should be aware the results are as small as a postage stamp - only 1/3 of the available image area will be used.