Best option I can think of is to buy a headlight with a large enough hole to relocate all the wiring to the new bucket. Fitting it all under the tank would be a nightmare, and then you need to worry about weatherproofing the connectors, and keeping it all away from the hot engine. Do you have a particular headlight in mind, or just a smaller one off another bike? Chances are if it's from another bike it'll also have a large enough hole for the connectors to pass through.
Matt
