I think you will find that most LED headlights use a lot less power than any of the original or halogen replacement and generate a brighter whiter light. They are often sold as say 55watts, but that usually means the equivalent light to an older style 55w bulb. There are available on ebay, and other places, typically in 7" (stock on most bikes) and smaller 5.75" sizes. I have used both on different project bikes. You can usually buy the same units off ebay as from specialty storestypically at a significant saving.
Having tested a few different units, some have a bright and less bright set up which isn't exactly what you need and isn't DOT approved but may be suitable for your needs. A good quality LED with correct beam cutoff might be harder to find and will probably come from Europe with a much higher price tag.
Stay away from high power halogen bulbs or HID (High Intensity Discharge) type lights which will over tax your electrical system. And consider wiring in a relay so that the headlight gets all its power more or less directly from the battery without overworking the switches.