For night riding your experience is made a bit better with a bright night light and you tend to have less trees running out in front of you.
I am looking at making a mountain bike light. This consists of a sealed lead acid battery, halogen light (available in 20 – 50W) battery charger. Could be some extras if you want like switches and connectors (so you can change bulbs). The idea with these things is you put the battery in your bag and the light attaches to the top of you helmet.
All up I would say they can be built for $60 - $70 but can let you know exact pricing closer to the time.
Let me know if you are keen on one because I am looking at buying parts in the next day or two
Craig
021 04 00 989