A view of the bare bracket. The aluminum stock material I happened to find is 6 mm thick. The thumbscrew is sold by camera shops - this particular one is a German made HAMA brand. They come in different lengths. I chose one long enough to pass through the bracket material so that its threaded portion just fits the depth of the socket on the camera. Only the first third of the shank's length down from the tip is threaded, the rest is cut back and therefore the screw, once inserted through the threaded hole in the bracket, is effectively secured against loss.

Of course I could have cut back quite some surplus material from the finished bracket to make it both lighter and easier to stow in a camera bag. But as I said - this was a quick job, to be done just a couple of days before leaving for an important trip.