Acrylic plastic is also called plexiglass (rather, plexiglass is a brand of acrylic plastic, but you've probably heard that name more often). If you know what plexiglass is, you can imagine how thick/hard it'd be to cut.
It can be found sometimes at automotive or construction type stores, I would think, or specialty plastics stores (TAP in California, I think). You can order it online, but only in huge sheets. And even then, the most popular colors you're going to find are clear, maybe one or two translucent colors, opaque white, and opaque black. Kamina's color is gonna be hard to find.
You CAN however, paint it, I asked this relative question a little time back and got an answer here
, so you can read through this thread a little more and see what you can get out of it.