I have a Phil Mill II and I used the shoulder screws from McMaster Carr (Part Number: 91259A634 I think) to attach a roller chain sprocket. I had it welded on at an exhaust shop for $5.
My setup is chain driven from a bicycle, but it's not really an ideal setup because of the side load that's put on the bushing. Works for now but I'll probably change it in the future. Here's the write-up...http://www.homebrewtalk.com/f51/not-drill-112378/
You could try a v-belt pulley from this link McMaster-Carr
Just match the belt size, bore size, and pulley diameter.