Check out or even better call Herbie's Audio Lab, he has somethings that should work. I would think his Grundgebuster dots may work.
Decoupling the Platter from the Subplatter
I have a Pro-Ject RM 6 SB and would like to place a silicone, rubber, cork or other resonance-reducing material between the platter and subplatter. The subplatter is acrylic and the platter is made of a thick 8-pound MDF material with vinyl on the record playing surface. Anyone tried this? Recommendations? Thanks in advance.