DV Info Net - External battery pack for FS-CV (or FS-4?)

Has anybody found a good external battery pack solution for the FS-CV (or for the FS-4 for that matter?)

The problem with the FS-CV specifically is: (a) there is no extended capacity battery pack available for it, (b) there is no separate battery charger available for it--you have to load them into the FS-CV to charge them. :( The standard capacity battery is rated for 180 minutes/3 hours so, for a six hours shoot -- to be safe -- you'd need three batteries for each FS-CV

The only (not very good) option seems to be to buy several standard capacity batteries and try and recharge them overnight. I have three FS-CVs (for three XLH1s), so that means "recharge hell" for nine batteries given that I'm shooting for five our six hours a day in the field and then need to "empty" the FS-CVs at the end of the day.

Has anyone found a suitable belt pack that will allow me to drive an FS-CV for seven hours? (Which is roughly the HDV capacity of the FC-CV.) I have a feeling that I'll need to make one up by doing a cable-ectomy on existing battery pack, eg. Bescor.

It needs 11-18 VDC, 7.5 watts. (That is, at, say 12v, 0.625 amps.) So I'd need about a 50 watt hour pack. (Visions of dragging a sealed lead acid battery around on a little cart behind me.... Lithium Ion would be much lighter!)

While I think of it, has anyone found a good belt pack for the FS-CV/4 too? Don't really want it on the camera because of the increased carry weight!

Thanks in advance
Andy