The best online site i found so far is....
www.superbrightleds.com
They all typically run on the 3.7 typical volts...so any watch battery is decent. Also they have multi intensitys depending on the viewing angle...I would use like 15-18 degree for head lights, and maybe 30 degree LEDs for a neon underglow...remember from the real customizers world...if you can see the source of the light from the glow...you lose.