The only thing I haven't figured out is how to make some sort of diffuser.
Update: Upon further inspection it looks like the power supply wont work as the leds draw more current than the power supply puts out. At least from the 12 volt side.
Last couple of pictures are of the plexi I bought and sanded on both sides. It was then tapped to the underside of the scanners glass. I guess I'll find out how good it works when I finally use it.