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I just figured out how to salvage my SX-70 film! I guess it could work for any Polaroid type film if you have any just sitting there with dead batteries.
1. Find an empty cassette with working batteries. In my case I happen to have a 600 type one left in my 600 Polaroid.
2. In total darkness, load the film into this cassette.
3. The top piece will be spit out when you load the cassette into the camera. So either put a used Polaroid on top or if you have it, the guard from the original pack.