I like the Three-On Lathe Mandrel and Bowl Buffs from Beall Tool Co.http://www.bealltool.com/products/buffing/
The problem is that they are made to be driven with the morse taper in a lathe headstock. You could get the set of wheels and compounds without the mandrel and put them on some 5/8" threaded rod. You would need the Shopsmith Keyless Chuck, which has a 5/8" capacity, or some other method of chucking the rod. If you are turning bowls, you may already have a four jaw chuck which would also work. The threaded rod would also need a dimple or hole in the opposite end for a live center.
A simpler, but more time consuming solution is to get the Wood Buff Kit, and mount each wheel separately.