Just a warning, I bought a couple of these lights a while ago, and I found the light from the 20W bulb about equal to the light from my 10W Trail Rat, and found that I preferred the light from my old 15W Niterider that took 5 D batteries (I used nimh rechargeables making it equivalent to a 6V battery pack) to the light coming from the 20W on this website. You may have a different experience with this.
The LED bulb you mentioned appears to be a 12V replacement, so I don't think it would work with a 6V battery. Also, 80 lumens is very dim. I'm pretty sure a 10W halogen would normally be putting out at least 200 lumens.
I realize this is a really old thread, but I'm still running a Vistalite Nightstick and thought an update might help anyone else who is in the same boat. I'm limping this light along since the improvements in lighting systems from year to year are so dramatic, and I'm waiting for Lighting Nirvana™. If there are any other cheapskates out there like me, enjoy this public service message.
I have the earlier-generation version (yellow button, 15W bulb, dual NiMH batteries) and just bought a few replacement bulbs from batteryspace.com. I bought three 6V MR11 bulbs: 15W 12°, 15W 24°, and 20W 12°.
Only the 15W 24° fits cleanly in the Nightstick head. While the diameter and total length of the bulb is fine, the 12° bulbs have a slightly longer plastic housing (and correspondingly shorter metal leads) than the bulb that was in there. That plastic housing bumps into the terminals on the switch, preventing the light head from being closed properly. The 15W 24° bulb does fit well.
They can be made to fit by unscrewing the switch housing slightly from inside the light head. This increases the spacing between the front of the housing and the rear. This does mean that the housing is much more susceptible to water getting inside, but seems to be otherwise OK. Waterproofing the light head with caulk would probably work.
Last edited by Celos; 12-12-08 at 12:31 AM.