I have these 4" headlights mounted on a homemade light bar. They are powered from the battery via a fuse and on/off switch, then through two relays, one for the high beam and one for the low beam. These relays are controlled by the high and low beam wires that feed the stock headlight.
http://www.jpcycles.com/product/3100278These lights each also include a 5W wedge bulb that you can wire to be on continuously if you wish.

For other photos, including the light pattern, see
http://photo.vrccservices.com/thumbnails.php?album=701. The only complaint I have is that, as with many motorcycle headlights, the angle between the low beam light pattern and the high beam light pattern is a little too large. That is, when the high beams are properly aimed down the road, the low beams are aimed too close to the bike for my liking.