I put a while light behind the red lens on my TT and it works OK. I got the bulbs at Wall Mart and they fit the standard socket. They are sold as replacements for standard taillight bulbs. I put one in at a time so I could compare results then I stood back and watched. They do light up quicker but, the ones I have are not any brighter.
If you find some brighter ones let me know. The tail lights on my TT are hard to see in bright daylight and I sure wish they were brighter.