There are a few folks that make their own, but not a lot that sell just toneboards. The time it takes to fabricate a custom made toneboard out of a rod of delrin usually isn't very conducive for how much folks are willing to pay for predator toneboards. If toneboards take an hour or two to make and tune, and the going price for a toneboard is $3-5, you can see why folks don't sell too many. There are a few folks out there that sell toneboards, but most are molded boards or boards that are cnc'd that don't take much time to make.
Making your own is very rewarding. There are a couple of tutorials here on how to make them. If you have any questions about making them, just ask away. Folks are very willing to help out.
Brian