Nikon 6AA Battery Pack - Grip # MB-E5000
More about the MB-E5000 when it finally becomes available
The 7.2 volt
Maha PowerBank # DPB140LI Not so much as a review as
my experiences using it on location in the slot canyons at Upper
Antelope Canyon. It worked perfectly when my CoolPix 5000 battery died
during a five hour shooting session.
and for those who want to do it yourself: Radio Shack's Battery Pack and Charger: 23-322