[HamWAN PSDR] Where does one buy these V-Bolt clamps cheaply?

I'm thinking about $2.50/ea would be nice. Muffler clamps are NOT adequate. Muffler clamps have 2 semi-circle contact surfaces, and if the pipe is slightly smaller than the clamp, this creates a 2-point contact which causes rocking action. Gross. The nice toothed and V-angled designs here are the bomb. Soup for scale. :) --Bart