Order one of these (or something similar) and JB Weld it to the frame. I haven't done it myself, but Doohickie did it to an '87 Prelude that I now own and it seems to be doing fine.

Or take it to a frame builder and have them do it.

Or use a clamp-on guide.

http://www.cycle-frames.com/bicycle-...E-2-LOOPS.html