I want to get some shrink plastic. Any advice?

If you get a take out box made of clear plastic with the recyle 6 sign on it, you can draw on that, i suggest using sharpie and if you want to use colored pencils, rough it up with sand paper. (remember it'll shrink in the oven to about 1/6 of the original size and the colors with intensify so don't use dark colors on your original or else it'll come out black) When you cut it out I also suggest you do so with manicure scizzors, and never "snip" or else the plastic will crack. Cut with the scissors so that the scissors haven't closed all the way. Heat your oven to 350. Then you would place a piece of paper from a brown paper bag from the grocery on a cookie sheet, place the plastic on it. and bake for about 3 1/2 minutes. they'll curl in the oven, but they'll flatten out once they shrink and cool. take out, and wait to cool.
I hope this helped a bit! I learned all this from this site if I wasn't clear in some places: http://www.curbly.com/chrisjob/posts/2252-diy-shrinky-dinks
Good luck and have fun!