They are really easy to make, we just sort of worked it out after reading a bit about it on here I think (some thread about a guy making his own housing - it looked great)
The most expensive part was the battery, you can go up to 12v 4700 mA l-ion batteries fairly easily but you need to get a specific charger too.We just used a NiMH pack.
They are pretty ulgy though, we bought a B&Q garden light and just wired the lamp though a switch to a "tamiya connector" which fitted the battery.... we then gaffer taped the whole lot to the stem

. it was a test but it did blow away my BLT 9INE. there is no focused beam though but I preferred that.
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Still wandering about....
Early Hope Disc Info... -
Xizang Serial Numbers... My Bikes:
1992 Xizang -
2000 Gazelle Superbe - 1983 Raleigh Mk II MiniBurner - 1995 Schwinn Klunker - 1996 Orange P7 - 1998 Specialized Rockhopper -
miniKen's Konalized Moderns: Genesis Caribou Mk1 Fatty - Pivot 5.1 Bouncy