Depending on the required tolerances, they look to be fairly loose from here, you could, as others have suggested, weld a piece of pipe to some flat bar and use a grinder to rough out the teeth, then finish with files. To mark out the teeth, you could print out a saw tooth pattern with 4 teeth that total the circumference of whatever pipe you use, then glue it on and cut/file to the lines. You should be able to get well within 20 thou tolerance. You could spend ages stuffing around to get a really good fit, but that's probably not required. Ideally, the pipe would be from some sort of high carbon steel so you could heat treat it. At home, that would be done by heating the pipe end to a cherry red (until it is no longer magnetic) then quenching in either oil or water, oil probably better unless you know that the steel is water quenching, then stick it in a toaster over for a few hours. But, if this doesn't see heavy use, you will likely be fine without hardening the steel. Whatever you make will likely be significantly better than the diecast crap the original was made from.