Weird about the Walthers one -- I searched their site for semaphores and that one didn't come up yesterday, just the OOS ones.
After looking at photos, it seems like these are really simple to make, I just have to get the correct size arm and lens assembly. They won't need to operate because they are going to be placed at a former crossing of two railroads, with one line gone and only a spur to serve on the other side of the diamond. So two will be in permanent "stop" positions and two "clear".