PVC would work. I use it a lot for the crafting stuff I do for cosplay props. However, you do not need to buy it in pipe form - you can get sheet PVC in various thicknesses from places that make outdoor advertisements and signs. Just google "PVC sheet in ________" (insert your city name) and you should find it. All you need to work with PVC is a heat gun and a Stanley knife.I recall someone using PVC pipe. Cutting it lengthwise, then heating it to make it flat. cut to desired shape, the heat it again and form it to the mold.