I have plans to cut out my own blue and pink stencils from wood because I will only have to use them one or two times and do not need them to last forever. If there was a source for cheap thick plastic or cheap thin metal sheets I would use those instead, just because.
I am working on vectorizing the black layer of Ms. Pac-Man art right now for my silk screen.. and it is taking much longer than I expected, so it will be a while before I have to worry about the stencils, but thats the plan lol.