***UPDATE 3/2009*** My original HIRs are still going strong over 2 years later.
***UPDATE 12/2007***: The price of the JD bulbs are no longer $12, current pricing is in the $25-$30 range, there are also other sources for the same bulbs in that price range.
I bought the John Deere HIR bulbs, I used
http://jdparts.deere.com/ to order them for $12.50 each. I actually had to call the dealer and reorder as they have never had anyone order over the web and had deleted the email they got with the order from the jdparts website.
These are John Deere part number AH211917. They replace the low beam lights, and are also known as 9012 bulbs. What I got when I picked them up, was Toshiba bulbs which made in China (PRC). The printing on them says: Toshiba HIR2 12V 55W, and DOT 9012. They do require you to trim one tab, which you can do with wire cutters, or some other implement on a handy leatherman. I replaced my dead stock bulb today, and the HIR is definitely brighter, though I have yet to see them at night. I will try to get pics of that later.
**Stock/old** bulb below: