Measure the rear spacing as well as the front. You really shouldn't have a problem finding rims/hubs with that spacing. 120 rear/100 front? Do you have a local bike co-op around that sells used parts? I have been known to buy a complete used bike for parts. Even just a stem once! Maybe thats an option. Then sell the frame and fork to pay for the paint.
If its too narrow out back you can spread the rear. It's called cold setting and its pretty easy to do. Hell, if you were local I'd give ya a set of alloy 27's and if they didn't fit I'd make 'em!