Other World Computing an Newer Tech are shipping battery replacements for G3 laptops. The NuPower replacement battery is compatible with the G3 Pismo and Lombard books, and are designed to extend battery life almost 40% over the standard battery. According to Other World Computing:
Newer Technology, Inc. (NewerTech() and Other World Computing (OWC) today introduced an extra high-capacity NuPower replacement battery compatible with the PowerBook G3 FireWire (2000/Pismo) and PowerBook G3 Lombard (1999/Bronze Keyboard) models.
Utilizing the latest Lithium-Ion (Li-Ion) cell technology, this new 6600mAH PowerBook battery provides 37.5 percent more capacity than the Apple stock battery for PowerBook G3 Lombard and FireWire models.
You can find more information about the NuPaower battery replacement at the Other World Computing Web site. The NuPower battery replacment is available for US$159.95.