I have a Sony camcorder too and looked at getting the 12 vdc battery charger. I about choked on the price. Since I already had an 12 vdc inverter I just use that with the AC charger cord that came with my camcorder. Plus I Can use it to power other 120 vac stuff I have. You can get 12vdc inverters at WalMart for about $30.00. The Sony 12 vdc charger was $60.00 if I remember right.
I take my sony digital camera and camcorder everywhere we go. I purchased a 20w inverter from Circuit City. Costco carries them now too.
it cost around $20. It plugs into the cigarette lighter and has 2 110v (regular wall-type) outputs.
I usually recharge my batteries while on the road, as well as overnight. I can also run my laptop off of it. I would also recommend looking into a "AA battery pack" for the sony video camera. Not sure if the new Digi-Cams have them, but the older 8mm do. It is a "battery pack" that takes AA batteries. Great for getting that extra 10 minutes to 1 hour of video when you don't have an extra rechargeable battery.