I had a really odd idea in my head, and I'm wondering if it might work. The roll film back fits very nicely into the camera when the spring back is removed. There are large flat surfaces on both sides of the camera. Suppose I cleaned both the camera and the holder carefully, and used a bit of silicone cement. Because the joint would be accessible from the side, a careful insertion of a thin blade would allow one to remove the back if necessary but it would likely be enough to hold the back on the camera for normal use.