I'll second the recommendation of Dealextreme. Specifically I recommend sku 15691. It is $35.90! I have tried several from them and this is the best by far. The flashlight says "900 lumens" on the casing but that is overly optimistic. It has an honest 450-500 lumens. It uses the Seoul p7 which actually has 4 leds on a single die.
http://www.dealextreme.com/details.dx/sku.15691
I get about 75 minutes of runtime from one 18650 cell & then it dims significantly over the next 30 min. I carry an extra 18650 cell in my pocket on longer rides. Dealextreme also has a mount which is a perfect fit. I use this mount for riding some blue off road paths on my mountain bike (Santos Trail) -- no problem in many months of riding. The light snaps right off when I reach my destination. The mount is strong and costs $1.90. http://www.dealextreme.com/details.dx/sku.8274
I purchased a set of two 2500mAh unprotected 18650s for $9.00 http://www.dealextreme.com/details.dx/sku.6979
and a 2 hour charger for $6.71. https://www.dealextreme.com/details.dx/sku.936
Putting it together:
Aurora SSC P7 flashlight - $35.80
Mount - $1.90
18650 batteries (2) - $9.00
Charger - $6.71
Total = $53.41
That's the shipped cost
Not bad for approximately 500 lumens. With your budget you could get two and have an honest 1,000 lumens. The lithium batteries are light, and the whole setup is surprisingly lightweight, significantly lighter than my Fenix l2d Q5 (which runs on 2 aas). The light is reasonably weatherproof and although it gets pretty warm, it worked fine for me during the past Florida summer. The spill and beam are perfect for riding. Plenty of throw & distance, lots of light for peripheral objects. Point it down a little and motorists do not get upset. I ride it on the road regularly. Believe me, I get noticed. It is a good feeling to have an oncoming motorist dim down from high beams from a distant hill. I get that all the time.
Here is pic on my bike: