If you're gonna pay to have it done, then any welding/fab shop could do it. The prices will vary depending on the person and shop. You should be able to find a neighbor, friend or relative that's capable, but I would try to have them teach me how to do it, if I were you..
If you really can't find anyone or you don't have the money, you could always cut the head off and bolt another one in it's place. Make your cuts back on the frome, and cut another head off of a different bike,that's close in style, at about the same place. Now find a couple of pieces of metal tubes that will fit tightly inside your bikes frame. Use this to sleeve the frames together tight. Now drill at least two holes through both sections (the frame and the new head tube areas). Get bolts that fit fairly tight in the holes and tighten them up. The bike should be safe to ride. After you've ridden a few miles, go back and retighten the bolts just to be safe.
Hope this helps. You can eventually get some fancy nuts and bolts to spiffy up the bike.
