Hi Matt, are you looking to power the mount in the field or at home? If the latter, I'd recommend looking at getting a suitable DC power supply (240V AC to 12V DC) rated at 5Amps or better. There are already a few threads in this section which outline what options you have in that area.
If the former, as has been already mentioned a deep cycle marine or caravan type of battery is what you're after. I use a 75AH deep cylce for that (which I also use for camping) but I'll probably be upgrading to a larger capacity soon.
cheers
