NOS number for GM part for entire assembly is 22048604. If you go this route, be prepared to shell out $$$. There's one on ebay right now for $400. As pointed out, the cable is crap. Old and brittle and will snap. You can tell it's toast when it tries to retract and the motor keeps running forever...
You can still find the masts here and there with the nylon cable and antenna (you mount it to your motor) part number 22048583 (non-CB version). Again, big $$ if you find them. Crappy cable and all.