I think what KMCA is talking about are the aluminum grip fillers that EGW used to sell a really long time ago. You screwed these in the gap behind where the grips mounted, filed off the screw bosses for the grips and then covered the whole shabang with grip tape. These fillers were nice, I've got a pair somewhere that I never mounted, but liked the way they filled the back of the frame.
ETA, I've got a couple of pair of the VZ grips, one set for my Para and a set for my SS. The grips for the Para are no where near as grippy as the SS grips. They are nice looking, they just don't seem to grip any better than the grip tape I've put on my standard Para grips.