First off, your gear may not actually run on 120 volts. Virtually all of the devices we use have step down transformers...what we commonly refer to as power supplies. Look at any external power brick, and it will tell you what it outputs to the device that it powers. The UFX has a built in power supply, though. So, it's not like you can bypass it without having someone make some serious modifications to the gear. That's not to say it's impossible, but it goes way beyond my knowledge as to how it could be done.
As far as field power solutions that don't require modding, I don't really know. Maybe Stuart Cody can give you some ideas. He specializes in batteries for extreme conditions film-making. It may be something out of his expertise as well, but he's a far better starting point than I am.