If you want to make your own, have a bit of a google on "homebrew bike lights" or derivatives of. There are at least half a dozen sites doing step by step guides on making your own, some even have lists of parts and wiring diagrams etc.
Biggest issues are getting a case, the optics and sealing.
Some of the homebrew people will provide you with these.
And FWIW, two of the UK based homebrew people have actually turned it into a proper business.
http://troutie.com/
and
http://four4th.co.uk/
I got an exodus from four4th, and its PROPER bright, i have to be careful not to point it at anyone when we stop as it may well boil their eyeballs.
And to be frank, some of trouties stuff is mental, he recently built a 7000+ lumen light out of leftovers, just for fun. Can't ride in front of him in case your clothes and hair catch fire.