Jim,
I'm sure someone like Georgia Jim would be able to complete this task. My only question would be one of economic feasability. Unless this happens to be a chunk of exhibition grade walnut (doesn't look like it), It would probably be better to either sell it to a do-it-yourselfer, then buy another grip; or get himself a few rasps, and whittle out his own version of a custom grip.
Having someone else do the work would probably put it tn the costs-more-than-it's-worth range. JMHO.