I got this 12V 35Ah AGM deep-cycle battery from Ebay for $85 shipped. It seems to have gone up in price a little with the falling Aussie dollar:
http://www.ebay.com.au/itm/PDC12350N...b4bc5e8&_uhb=1
I haven't even had a chance to use it yet but I have complete faith in it lasting the night.
Edit: I'm not running a CCD though, they suck the juice!
Cheers,
Cam