If you have any basic soldering skills or hacking skills, hack a charging sled for the Sony np-f750 / np-f950 batteries (the same batteries used by the Sound Devices 722/702) and use those batteries.
The SD 702/722 style batteries are 7.2v, which works great for the V3, and are very easy and cheap to come by. You can get knock-off batteries of this style that are 7.2v and 6600mah for under $20 or so. Way easier to find than DVD batteries, and a lot smaller.
Get a charger like this one:
http://www.ebay.com/itm/110763237927Or better yet, get two -- one for charging, and one "charger" for hacking. I'm not recommending this ebay vendor (though they may be fine) it was just the first picture I could find. This charger bed is "universal", and different "battery sleds" can be inserted into the charger. The sleds are specific to the battery type (in this case, the Sony NP-F750), but the charger is made to accept many different sleds.
From the picture on the ebay auction, you can see the outline of the battery "sled". This sled pops out of the charger. It doesn't have any electronics (those are all in the charger body) -- just pull the sled out of the charger and hack into the sled to attach the right V3 coax power cable (a locking Switchcraft connector, I forgot the part number). Use the sled to use the Sony camera batteries or generic equivalents (read through the 722 threads for ideas on specific batteries, but they are plentiful, high capacity, and cheap). Use the second, non-hacked charger as your actual battery charger.
This probably sounds worse than it is, but it is an easy hack. You can get these chargers for like $15 for 5 of them. Someone needs to get Ted to make this as a regular product. I use the 722 batteries all the time with my V3 and a sled like this. Cheap, large capacity, reliably, small, and light -- what's not to love?