I brought a helmet camera kit from eysepyworld - check www.helmetcameras.com.au
the kit itself was approx $500AU when I got mine, it included crash box SLA battery that gives up to 10Hrs rec time, all cables and chargers etc. In addition you need to have a small camcorder with RCA input, so a second hand one from cash converters at the time about $400AU did the job.
downside - external wires get a hammering, had them replaced a month ago, also had a dodgy rca or power plug (which i suspect was faulty when I brought it, but eventually failed due to the cable wisting) and had to do sme work on the mic, tried all sorts to cut out the wind interference, like polar fleece sock over it, and also tried sponge foam, connie zip tied over to wterproof it, eventually settled for a plastic band-aid and the polar fleece, which worked well.
upgraded the lense to a wide angle - $20AU and made some mounting rigs out of alloy myself, which have given some interesting angles, trying to get bars and side of helmet into the frame for some perspective and scale.
Quality appears much the same (nice footage BTW), but most of my footage is in low light (winter riding).
you can check mine out at youtube, just search for 'awilksch'.