I always thought it would be handy..but cost of supplies (the plastic line) might be more than what you're making if found elsewhere made from some other material. I believe this is the case with templates..in the first place, plexiglass is cheap at your local box store..you can get a zillion templates out of one piece. You can cut it with a scroll saw, jig saw, oscillating saw, dremel tool, and probably a lot of other things. If you need it to be thicker, you just glue 2 pieces together for a thick template, cheaper than buying the thicker plexiglass sheets. I clamp a metal straight edge to mine, then use the dremel tool score a line, then I fill that line in with permanent marker.
I would try the library, though..might be fun !!