Treso offers a short starter kit, which has all the individual parts for a short starter: ball, shaft, brass tip for the shaft, and the short starter button. Easy, peasey. But, rumors have it that Treso has pretty much shut down, so those kits might be a little more difficult to find.
For the real do it yourselfers, a piece of 3/8" or 7/16" brass rod, 6" or 7" long is a good place to start. 3/8" rod would be easier to find, probably at a good hardware store.
If you don't have a metal lathe, a wood lathe would be OK. So, go down to your local metal working supply business and buy a 7/16" ball mill. High speed steel will be OK, as you are working with brass, not steel rod. You want the next size larger than the material you are working with. A 3/8" ball mill will make a deeper concave opening than you want. So, mount the brass rod in the chuck and the ball mill in the tailstock, bring it up close to the rod, and feed the ball mill into the rod end and that will give you a nicely indented tip. Cut that end off at about 1/2" or so long and there is your short starter button. Repeat the process with the brass rod and you will have the long starter. Pretty basic. If you are working with a metal lathe, you can knurl the rod for a better grip when you epoxy the rod into the antler.
Hope you understand these instructions. Enjoy.
John (Bigsmoke)