Good luck!!
They're all pretty much long gone by now, although CMSNL have SOME of the parts, at extortionate prices.
If it's any help, I fitted a good used system from a CB900 custom to my '79 Limited Edition - Still 4-1 and looks spot-on.
Maz
'76 CB500T
'75 GL1000 'Wing
'79 CB750L
'90 FJ1200
'93 GS500E
In a little place called Bexley, Kent, UK (Just south of London!)