Look at http://nrgresearch.com/ for the NiCad light weight belts;
Bescor for less expensive heavier Lead Acid belts. We make step down 12v to 7.2V voltage converters.
HTH
BTW, I have one of your chargers and love it. Sadly an AC on a set pulled a battery straight off broke the little tabs on one of the mounts. It still works, but it doesn't "lock" the battery in place like it's supposed to.
Another question related to the 7.2v batteries. Is there an external mount to relocate the battery? Using that same mount could I power both the camera and monitor off a single battery, or would I need two mounts. I've got a glidecam 4000 and a nebtek monitor, and want to relocate the monitor and batteries to the bottom of the sled to use as counterweights.
No problem, you out of only $15 plus S/H for the new plate - send the charger in, it will take a day or 2 to turn around.
I am not sure about the mount, but electrically you would drain the battery too fast to be useful :-(