Rotating Tube Rings

I am interested in rotating tube rings for EQ mounted scopes like the Cave Astrola or Criteron types. Anyone know of a source for these? Anyone use this type of a set up? It seams to me that this would be a very desirable feature in an EQ mounted scope.
Thanks
Craig

Rockler woodworking stores sell a ball-bearing Lazy Susan turntable with an inside diameter just shy of 15" for $55. This is a continuous ring, not split. It's very solidly constructed and weighs 3 1/2 lbs. I bought one and am planning to use it to construct a rotating eyepiece section on my 14" Newtonian.

Also on the subject of rings, I'm starting work on a 20" equatorial mounted truss tube scope with a rotating upper cage. I built a ring roller and have been bending a piece of 3/4 x 1/8 inch aluminum angle into a 24" diameter ring (it's a lot of work!)

Thanks for the input everyone, I'm thinking about making a set for myself more as a winter time project than anything else.