I'm trying to find a source for white plastic for the vacuum former to make eyes and noses. What kinds do you use, how thick are they and where do you buy them from? Someone said you can use garage sale signs, which I tried with bad results. The area with the printing was all messed up, and they are too thin.

I read that these all work, but I'm not sure which is best or where to get them or what thickness:
acrylonitrile-butadiene-styrene copolymer (ABS), high-impact polystyrene (HIPS), high density polyethylene (HDPE), high molecular weight polyethylene (HMWPE), polypropylene (PP), polyvinyl chloride (PVC), polymethyl methacrylate (or "acrylic") (PMMA), and polyethylene terephthalate modified with CHDM (PETG)

Any help is greatly appreciated. Thanks!

I found one source for plastic via Google: https://www.professionalplastics.com/PlasticVacuum-Forming  There where others but that was the first.  You might want to try Google along with your location to see if maybe there is some local source.  You might also be able to find a local source using this site. https://www.thomasnet.com/  The beauty of finding a local source is that you could go in and talk with them to let them know what you are doing... you might even be able to get some scraps from them to experiment with. We have a local company that sells foam in large sheets.  They always end up with scrap from custom orders and they have a large bin they throw it in. They would often let us have it for free or a very small cost.

Thanks Shawn for the tips. There's a TAP plastics in Seattle, so I'll go talk with them.