These are the best prices that I've found.

1) Polarizing filters. Flatten the sheets and then cut into the sizes you want.
- 17” wide, $15.00/foot
- http://www.polarization.com

2) Cardboard framed glasses for 3-D movie viewing, the lenses are at +/- 45 degrees. They look silly and help when you are trying to deal with three filters. Your hands hold one each and your head the third.
- $0.50 each
- http://www.rainbowsymphonystore.com

3) Fancier Glasses for the new 3-D films. I don't know where to buy them. I asked the manager at a nearby theatre if I could have some of the used glasses and he said yes. It seems he is a big fan of physics and had some questions about string theory that he wanted to discuss!

4) Calcite crystals (Icelandic Spar). These are delicate, don't let your students drop them.
- $6.00 each
- http://www.teachersource.com