Matt Denison and I spent an afternoon in my shop trying to duplicate the old turned up metal rear sights. Modern steel has to be heated to a very high temperature to do it, but wrought iron was pretty simple to turn up.
A good idea to serve the purpose. I've used epoxy that comes off with a little heat but a magnet is a better idea. I've seen a couple of original trade guns that had a rear sight made by using a sharp chisel to curl some metal up and then file a notch in it. These were later percussion guns from British Columbia. Probably too low to be of much use.