they did sell a ball end attachment but I think its discontinued now. ... Darex E 90
Keep your eyes open. I got a used Darex E 90 on eBay *with* the ball end mill attachment in addition to the standard straight end mill attachment. It also came with about 35 collets and three grinding wheels (two of which were new) and some other extras. They do not show up very often but they do show up.