Studio, there are many suitable inverters available out there. Here is one place: http://earthsolar.com/inverters.htm
(I can't vouch for them--I've never done business with them. I link to them as an example of what is available. I do know, however, that the brands they list are the "usual suspects" for bulletproof inverters of this sort.)
Pick something that runs off a 12V battery, is pure sine wave, and provides sufficient power for your equipment.
Alternatively, there are "automobile adapters" available for virtually all laptops that will power your laptop directly from any handy 12V battery.
B&H has substantial 12V batteries that can power quite a lot., that are intended for powering lights for TV news reporters and the like. IIRC, one brand is "Bescor." I have one of those batteries and an "automobile adapter" for my laptop, which is easily sufficient to run my laptop all day long.
There's a company out there called "iGo" that makes little power converters that are designed to essentially power everything from anything--one converter to power your laptop, cell phone, PDA, etc., from 120VAC, 12VDC cigarette-lighter connector, or from an airline connector, etc. (Or at least they did a ~3-4 years ago when last I looked at them.)