I've pretty much been using Eagnas PN-1012 clamps on my 6004, as well as the Dual clamps that look like the currently shipped Gamma clamps (like yours). My Dual clamps, don't have the bearings like yours does.
Someone told me Prince, Gamma and Alpha get thier current clamps from the same manufacturer. I think the new Alpha Ghost and Phnatom have the same clamps.
Machines: Gamma 6004 2-point w/ Wise 2086 & Babolat Sensor Dual