I use the TerraLux 300 (lifetime warranty) wider beam flashlight in a funky looking Chinese mount that actually works well with a little shade tree modification along with Eneloop rechargeable AA batts (2 required).




So March 2nd 2013 pricing is about $33 for the light, under $3 for the mount and $18 for the charger & 4 batteries. I've used this system for years (except I used the TerraLux 220 until the 300 came out) and it works well under 20mph on the street or smooth dirt trail. The light is bright, hold it in your hand & shine it in your eyes & you'll regret it for a few minutes.

1) Remove the pocket clip. Find the balance point of the flashlight & put that point in the center of the removable light mount and tighten the fastening knob.
2) Put the funky Chinese mount base on the bar, I use old inner tubes to make a bar spacer rather than what's supplied.
3) Slide the flashlight onto the mount, it will rotate left-right, use the handlebar mount fastener to get the up-down you want. Go look at it in the dark, freakin amazing isn't it? It seems more impressive aimed so the bottom of the beams dimmer halo is 3 feet in front in front of the tire/ground junction.
4) Now fix the wobbly nature of the mount by carefully sliding the light off the quick release mount so as not to disturb your L-R adjustment. Get some black electrical tape (45cents) and wrap 2 turns around the swivel portion of the base. Fold over & smooth & you don't even know it's there.

You now have a very good light for under 20mph use that doesn't blind oncoming, a mount (that you can duplicate for $3/bike, and 2 batts + 2 spare AND a charger for $54.45. For $36.45 you get the light & one mount, so I'm way under budget.
The mount is QR, just put a base on each bike & the light will go from any bike to another with a push on the front QR lever.
Other cyclists have been amazed by the price when they see the thing in action.
Is it as good as lights in the $150 & up range, absolutely not. Is it pretty freakin' impressive for $36.45? Absolutely.
Also, TerraLux is in the USA and does honor the warranty, we had one of six go out (older 220 model) & they sent a switch free of charge!