Kindle 1 batteries in stock now
Batteries for first-generation Kindle devices are available now from Amazon. These have been in and out of stock over the past few weeks.
Kindle 2 does not have a user-replaceable battery. But many Kindle 1 owners keep an extra battery or two around so they can keep their Kindles running even while on extended trips away from power sources.
The batteries are available for $19.99 from this Amazon page. Thanks to Steph H for the tip!