lasermygun.com [I DO NOT OWN THIS SITE OR ANY OF THEIR SERVICES]
I think it is $80 for one color- I'm not sure. Check the prices. IF you want your gun to look epic, I would get a color (for me silver, gold, or green) and then get a laser engraving stock design.
Looking for cheap guns around $150:
High end guns that you need to get rid of quick.
Dangerous Power Guns -Spyder's under 15
Cheap new-ish angel
Old Ego/Etek (2007+ please) - JT E-Icon