I found an Erickson single angle collet with proper length, proper diameter shank for only $149 +$25 collets, in MSC and I milled a slot in it for the model P drive pulley. I don't have any machines at home so I drove to my friend's house, who has a 24" drill press with an X-Y table on it and we cut the slot in it fairly easily. I now hold 0.0005" measured runout with a 1939 valve grinding machine. The collet conversion total cost less than $200
Here's a gallery showing what I did to convert it
Here is one quick picture of the finished product
That collet and shank are all one piece and I just got so lucky that I could order it with a 1.25" shank, and the shank was ground to a nice enough finish that with a light polish it was good enough for a bearing surface. I mis-used Erickson's collet in a way that just worked out really well.