Harbor Freight is where I got my first one. It was the largest and biggest. The one you may be thinking of with the heads on the edge have been seen at Hancocks and JOAnn's Pricey! I have a smaller like Harbor Freight but it cost more and was from Home Depot.
Originally Posted by
Blackberry
I have one that is metal and I got it at Harbor Freight which is basically a hardware store. I also buy my rotary cutting blades there which they list as blades for carpet cutters.