I don't have that bayonet, but I think those parts shouldn't be hard to make. Take the nut out (carefully to avoid splitting the wood) and find a metric screw with the right threads at a hardware store. Making the excutcheon should be a simple lathe job. I would make a drawing of the dimensions and see if you can find something that can be made to fit, or talk to a machine shop or a friendly neighbor who has some tools. I honestly think a gunsmith would charge too much.
Jim
