RE: Substitute for hot wire cutter
A lot of guys use SS fishing leader for their hot wire cutters. You'll need a bow for line anyways, so the only thing you're missing is the power supply. Do a google search on "foam cutting power supplies". There are lots of different ones out there, and they are relatively cheap and easy to make. Other than that, maybe if you tried one of those string saws that campers/canoeists bring along?
Brad