I use the Sylvania Silverstar H4 headlight bulb. The model H4ST is specifically designed for motorcycles and has a one year warrantee. MUCH brighter than stock. The car model H4 bulbs didn't last very well but the H4ST has been in for over a year and is still going strong. There is also a SilverStar sealed beam that I think is the correct size if you go that way, the H6024 SilverStar Sealed Beam Headlight. It's even a tiny bit brighter.
