Eddie,
You might want to check with Jackson Speaker Service. He might have what you are looking for. If not, one of those classic car junk yards in Phoenix might, and you can then rebuild it. I've had Jackson rebuild numerous original speakers and the quality of work is excellent. If you hit the junk yards, try to get the little grounding clip that goes with the speaker (for the rear single wire speaker).
Here's someone who sells a pretty decent repop.
http://www.turnswitch.com/speakers.htm
I'll check to see if I have any single wire 6 X 9's.
Phil Woj