A wall-mount power inlet and a piece of romex should do the trick. It'd be far more difficult to patch the drywall well than it would be to run the power, but even that's not difficult with a little patience. Of course, the farther away you put your UPS, the more hairy it gets. It is legal to run romex (nm) through the crawl space as long as you run it through the framing or along the framing and not under it, so that's another option to avoid cutting the drywall as much.