As I was changing the headlight bulb in my wife's '99 Corolla I noticed the base of the bulb looked very similar to the base of the bulb in my '86 Bayou 300. Mine had just burned out so I figured I would try it.
It turns out that a 9003 Halogen bulb is the same wattage and fits right into the 300 Bayou headlight. I haven't had a chance to try it at night but hopefully it will be as bright or brighter than the original.

 

Good luck. I hope you found a good alternative.