You could buy the pack film that they are designed for if you don't mind spending a lot of money on a few shots of expired instant film.
You could get a few shots of recent manufacture peel apart film from the.supersense.com/collections/instant-photography but it's 49 euro for 3 shots and it doesn't produce a usable negative. Though you might need to act quickly to get it because they only make small batches and not very frequently.
I used to use a similar back to single load sheets of new polaroid 600 in a darkbag but you'll need a compatible camera to process the film once you shoot it. It's a whole process but it's pretty fun if you like that kind of stuff.