This mod makes use of 2 Hella Angel Eyes - not originally designed for motorbike headlights, these do not have high- and low-beam settings. As a result this setup needs some wiring to allow dual headlights with one light on for low, and both on for high. The circuit is reproduced below.
The diode can be purchased from Radio Shack or Fry's. Diodes are like one way valves. It lets current go one way on not the other. It is necessary because the low wire will be hot when the high isn't. Without the diode the current would go from the white to the yellow line and light the high lamp when on low. However, you need that connection because the low wiring isn't hot when on high. So, without the diode you either have both lights on all the time, or only one lamp on for low and the other for high. Make sure to get at least a 12 volt diode, and to connect it in the correct orientation. The correct orientation is to put the stripe toward the low headlight.
Dominator headlights are available as a pair in either black or chrome finish. They have two 4" reflectors and run two H4 55/60W bulbs - as a result they will provide twice as much light as the stock headlight, but also draw twice as much power (~9A).
The Dominators come with a wiring harness meaning that they plug straight into the original headlight socket - although the wires are fairly long, meaning that a bit of a tidy-up with some black tape is required for neatness. They take very little work to install.
There are a couple of mounting options:
There are a number of stores online selling these headlights - often under different names, but they all appear to be the same product. www.streetfighterstore.co.uk seem to be the cheapest, but being a UK company shipping costs need to be factored in when making a cost comparison.