I have a model that I made years ago that would be perfect for this
project. It consists of two rings that were machined to lock
together. I made this on a simple Enco Compact 5 lathe/milling
machine. I used it to lock two haves of an egg together.
If you like, you may borrow this model to show a machinist in your
area. Anyone can do this job, and there is so little waste from the
machining operation that I wouldn’t worry about saving the scrap
(most machine shops don’t worry about saving the metal that is
removed). You can even check with a local hobby shop, since even a
hobby machinist would have no trouble making this.