From what I can find, you can buy a Rota-Dent toothbrush at Amazon for a fairly cheap price. They carry the electric model for $109.95 and have free shipping. This one has patented micro access technology.
1 Additional Answer
Sometimes you can purchase a Rota Dent Toothbrush from your dentist just as cheaply as you can anywhere else. The best place to get a Rota Dent Toothbrush online is at a website called Real Tooth Brush Deals. Their Rota Dent Toothbrushes are cheaper than Amazon's Marketplace.