I read your first post; what you look for is easily made. I have made/adapted backs for my cameras many times, and it is not rocket science to make one to work well. I am attaching a scan of my Graflex 6x7 rollfilm back with a slot that I cut in the edge (does not change the dimensions) so that it would key into my Wista 45SP's back. All you want is a way to "grab" the edges tight to the camera. My Wista had sliding steel retainers, while my Chamonix has rotating retainers. You can use porch door sliding bolts or any other similar hardware to achieve this.