Rubber suggestions

[t1mpani]

I have a Greco X-Plorer that I love, but it's difficult to work/chop with for extended periods because the micarta scales aren't up flush with the spine, and the handle is slightly on the thin side anyway. The handle screws have some extra room, so I'm thinking of just putting some slim hard rubber or resiprine material under the scales tha I can taper into the spine. Looking for suggestions on what material to use and especially where to get it. I'm looking for something between 1/16 and 1/8 inch thick.
Thanks,
t1