Crackedback used to have a machinist buddy that made them, but he stopped doing it years ago.
foursecondsflat makes them.
https://www.4secondsflat.com/MSD%20Distributor%20Tuning.htm
I just made my own out of aluminum rod.
The diameters apparently are...
0.386" = 14° and 0.394" = 10°
ID=...