Fenix L2D with the new Rebel LED (the same light previously suggested) with the lock block light holder thingie.
This light is unreal. I ran it tonight in very mixed lightying conditions (dusk, busy streets, semi-highway, rural backroads w and w/o streetlights) with my dinotte 200L 4AA (which I highly recomend!). I ran the 200L on low (100 lumens) and the Fenix I toggled between low and "turbo" to conserve energy. I also had a 3rd Fenix L2D with the original CREE LED which i was using too, but with the dinotte and the Fenix Rebel, the less powerful fenix was almost useless even on turbo.

The nice thing about the Fenix is to toggle between low (good to be seen by) and turbo (good to cruise at 15 mph or more on dark roads) all you do is twist the bezel a quater turn. I have the lock block strapped to the bezel/head of the Fenix light so to toggle between the 2 brightnesses, all i do is twist the back of the light and voila! low to turbo, turbo to low in half a second. A nice feature.

(with the dinotte on low and the fenix on turbo, i feel comfortable on dark roads descending at 30 mph, uing the turbo judiciously i will get 5.5-6 hours out of this lighting set up with 6 AA lithium disposables and a total system weight of way under a pound).

The Fenix is so light that you can mount it on your helmet if you get another one for your bars and barely notice it. Great for getting drivers' attention.

The lock block alows for multiple mounting options and is in my opinion as good as most "nornal" light mounting brackets but much easier to use and harder to brake.

This is the only choice I'd make at under 100 bucks.

Go to batteryspace.com to order nice rechargeable AA's and a nice recharger for around 20 beans.

-Leo