Just ordered a GoPro Battery BacPac from Amazon, 41% off. It will happily work with both the 1080p HD and HD2 cameras.

– Attaches to the back of the 1080p HD HERO camera
– 2X (approx) extended recording time
– Plugs into any USB charging source to charge your spare HD HERO batteries
– Charges 960p and 1080p HD HERO camera batteries
– Built in LED lights indicate battery power status

It charges up to 80 percent capacity in two hours when plugged into a computer USB, and one hour with a charger, making these units outstanding for any application where you need up to two times the battery life to capture all of the action. They include a waterproof door and a skeleton door for the HD Hero housing, as well as a USB cable.

GoPro Battery BacPac