This is not the AlBooks, but NewerTech is apparently actually shipping this item.
NewerTech Hi Capacity 7200mAh Lithium-Ion Battery
for PowerBook G3 Lombard (1999/bronze keyboard) & G3 Firewire (2000/aka Pismo)
-Replacement battery for the Powerbook G3 1999 "Lombard" & 2000 "Pismo" systems
-Directly replaces Apple parts M7318, M7385G/A
-50% increase in capacity over the original battery
-Li-Ion 10.8V, 7200mAh
-1 year warranty
If the dimensinos of the battery are about the same, maybe it won't be very long until we see a version for the AlBooks?