I made my own and it has come in handy. I went to Play It Again Sports and bought the best pair of old in line skate they had, which cost me $25 and gave me 8 wheels with all 16 bearings, two per wheel. I cheated and had the ShopBot operator at work cut my rings out of 3/4 plywood for me, not very good at cutting them with a jig saw. I have a Jet 1642 so my outside diameter was 16" and the rings are 1.5" thick. This centered the ring on my spindle. Not a difficult project, found a couple good pics on the net and went for it. Used wing nuts on the back side of the arms. I need to replace the washers on the either side of the wheels as they are too big and had to loosen the nuts so the bearings were being used.
I, also, enjoy building my tools, next project, a string steady rest and articulated hollowing arm.