As a guy who has not only sold, but used horse mats, I can honestly say that I think it could work. I assume you're thinking about a non-slip grip. If you have a scroll saw, or band saw, its easy to trim the large 4X6 mats down to what you need, and they're relatively inexpensive for what you're thinking about. You could get at least 100 knife handles from them. I'm not sure how a sander would react to the rubber, but I believe that a low grit, say 50 grit, sander would let you shape the rubber.