I paid $3.00 for this rear light and attached to my helmet with zip ties.
http://www.ebay.com/itm/NEW-12-LED-T...item43a573ef0b
I also run a Planet Bike Superflash Turbo on the rear. The whole attaching to the rear of the helmet with zipties was an experiment, and it didn't work, and the light fell out, my loss would only been a couple bucks.
However, to my amazing, the little el-cheapo rear light performed like a champ!!

My wife went for night time jog. I told her I would tag along so she can give me an idea on how the cheapo light performs. She said it was like a Christmas Tree!! She said it was very bright. I asked her how did it compare to the light under my seat, the Superflash? She said the cheapo $3.00 light was brighter..Now, I asked her this 3 times. Then I still didn't believe it, I had to get off the bike, take off the helmet, and told her to walk in front of me about 50 ft.. The little cheapo light was holding it own up against the PB Superflash Turbo.. I figure the cheapo light would be a disposable light. That means after the batteries run out, it would be no more good. If that happens, I still think I am getting more than my money's worth..
Even for the $3.00 the vender on Ebay has best offer.. So, me and my cheap self, I offered $2.50 for 2 more of them. The vendor accepted.. Going to attached this $2.50 wonder to all my helmets...
I run a PB Beamer on the front of my helmet too..