I have two eBay "tactical" flashlights on top, pointing forward. Having two gives a nice wide field of lighting. They're attached with hair ponytail bands, looped over one end of the flashlight, down into the helmet through a vent, back out through another vent and looped over the other end of the flashlight. This keeps them in place while allowing me to think they'll be break-away (stretch-away) in a helmet-skidding crash.
I've had these for a year. I got good runtime with disposable AAA cells (three each flashlight) but finally started using rechargeable 18650s (one per light). The runtime seems somewhat less and once they need charging the light output falls off fast, but they're very bright.
Flashlights were $12 for the pair; batteries $22 (that's two to use and two as hot spares), charger $15, hair bands $2. The downside is I look insectile or crablike with those two lights up there. I'd rather have the lights integrated like engine nacelles on a B-2, but I won't get that for $12.
I have both set to widest beam width, which overlaps about 20% in the middle. This is fine, it's like a brighter spot where I'm looking. I do wish I could diffuse the beam edges toward the sides, but when I tried a diffuser it cut the light output too much.
Anyway, this is working well for me.
