You can get these super bright tactical Cree led flashlights on the web for under $10 if you look around.
they are super bright, they has a flash setting and some of them have 5 different power settings.

I get them from a site in china for about $5 without batteries, but they are the. same thing.
this one is on amazon for $10

Outlite A100 Portable Ultra Bright LED Handheld Flashlight with Adjustable Focus and 5 Light Modes

then you can get a $3 bike flashlight mount and you are ready to go.

this is at least what my son and I did and they work great.
although i am going to make a Velcro strap to hold the light in in case it ever pops out. It hasn't but it seems like it will.