I noticed sone one is making and selling a percussion cap making die for about $25. On eBay. It looks very professionally made. The instructions say it is only for a snap cap use. I might check it out. It uses soda can or roasting pan metal. It produces a cap the same as my star board, or the 6 shooter die. The sell #10 or a #11 die
Oh and a musket cap die. It appears to be plastic so has a limited life.