The low beam on my Kawasaki burned out awhile back and I went shopping for a replacement.
The replacement bulb for a 2000 KZP is Kawasaki p/n 92069-1002. A local Kaw dealer and BikeBandit.com want $62.96 for that bulb. The stock bulb is a H4 (Halogen 4) 60/55W. This bulb is also known as a 9003 bulb. It's used on some automobiles as well as motorcycles.
That seemed like a lot of money for this little bulb so I ended up buying a couple from Napa online for $5.49 each plus $7.49 shipping. I would have bought them locally but none of the Napa auto parts stores had them in stock and they wanted me to pay shipping and then pick them up at the store. Made more sense to have them shipped to me.
I replaced the bulb and noticed it wasn't as bright as the one that had failed. I assumed the burned out bulb was stock but it turned out to be a H4 100/80W bulb. You can buy one of those at JC Whitney or Amazon etc. for 9 bucks. The description of the 100/80W bulb says it's for use in off-road conditions only. If I was doing much night driving I might go ahead and get one - it made a difference in road visibility and no one was flashing their high beams at me while I was driving with it - so I assume it wasn't blinding oncoming drivers or annoying them.
You can read about the H4 9003 designations on Wikipedia or at CandlePowerForums. The H4 comes in a range of wattage ratings e.g. 60/55W, 100/55W, 100/80W, 130/90W. This first number is the high beam and the second is for low.
I guess it pays to shop around and check to see that the part you are ordering is actually same as the the one on the bike. I never thought of going through the minor hassle of pulling the old bulb to make sure what wattage it was - I was more interested in riding and I had a high beam and a couple of driving lamps working.