Bought a set of used headlights for about 100 usd (shipping included, can't beat that price).
Opened them according to one of the guides. In my opinion starting at the top is easiest and makes less damage.
Anyway, I pained the underside with matte black, but because of the plastic it looks shiny.
I also bought a few neon case fans for a pc which had a blacklight cathode ring around them, unfortenately they were just too big for the project lens, so I just put one ring in the bottom. I love my glue-gun
Put everything back together and glued the top and bottom of the lights back, here's what it looks like, one pic with flash, one without. I hope I have the time to put them on my car tomorrow and get more pics