Mick,
In the search for the answer to this very question, I took one day two
months ago, and hit every local FLAPS in a 20 mile radius, and found
----NOTHING.
And I ain't talking Pep Boys, and Track, I'm talking NAPA, and every Mom
and Pop operation that has been around for eons.
I did find some older listings that did work at one time, but after
calling the manufacturers themselves, I found that all of the part
numbers that I had come up with were NLA.

I tried-----and  wound up with a $49.00 manual retract, from VW, and by
the way, it is a piece of flimsy garbage.
The mast shakes like it wants to blow off in a headwind, or at speed.
The Pep Boys antenna is one heck of allot sturdier, if a guy would just
stay out of carwashes.

Take a day off work, and check it out, see what you can locate.
I kinda like the solid mast idea myself.

Later,

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Terry--
74 Campmobile- (Clementine)
85 GL- ( Delilah)
86 BMW 325 ES- (Eva)