You nailed it with this answer.  I was looking to buy some.  That's awesome!  Thanks very much!

It's usually just called a (linear) polarizer or polarizing film. Are you interested in the chemical composition or do you just want to buy some? I wouldn't hold my breath for finding it locally, but it's readily available on line. First Google result for example: http://www.polarization.com/polarshop/
If you are on a zero budget or wish to have some fun, try doing a teardown of an old/broken monitor. You will find a sheet of polarizing film as one of the layers in the LCD panel.

Like the title says, can anyone tell me the name of the material polarizing film is generally made of and whether it's something that could easily be purchased at a local shop?

Thanks very much!