Home Depot and Lowes carry a nice selection of Velcro straps and adhesive backed Velcro. It is usually located in the hardware (bolts, nuts, fittings) area.

As for your question about material for templates. I use(d) hard balsa with a length of small diameter piano wire ca'd to the edge. After ca'ing the piano wire on, sand the outside edge with very fine sandpaper (600-1000 grit) and the nichrome cutting wire will slide in it very well.

Woodie
Team Acme LG
Team Blenderm