Can you buy one header?

If you've got a friend/coworker/teacher with a Mandrel Bender, have some new tubes bent up to replace the ones you need to fix.

Or weld in sections of pipe/tube to return the current headers back to their original layout. You've probably got 1-5/8" Headers, right? A stick (roughly 12') of 1-5/8" exhaust pipe is dirt cheap, even a half-stick would probably be more than you need to fix your header.