Sounds like you have a really nice car with lots of options!
The housings for rear speaker with rear defog are available reproduction from Mike at BE&A restoration parts. I haven't seen the reproduction piece in person because I have an original, but usually his stuff is top notch.
The clips that hold the wiring to the bracing behind the seat can be tough to find also. If you can't find them, you might try using dome light wiring clips that clip on the sail panel behind the headliner, or trim down some cuda roadlamp wiring clips which are also available from Mike at BE&A.
Tav
