Lot of options there. I use a H4 LED bulb from Cyclops, they appear to be sold out at this time. But . . . check in with them, they're showing restock on August 2nd. I like it a lot. Very bright with good pattern and didn't drain the wallet like other options.
GRiSO Ghetto forum has a whole lot of info about various bulbs, lamps and bucket conversions. Let your fingers do the waking.
Stock head light set is, you know, weak.