I just noticed today that disposable lighters are a great source of colored acrylic, plastic, carbon fiber, and whatever else. They cost only $1-2 for acrylic ones and $5 or so for a carbon fiber one. The acrylic is usually 1/8" thick or a bit more, although most have a divider piece that has to be sanded down. Just make sure to empty the fluid completely before cutting into it. Each lighter will make about 4-6 wedges.