Go to a junkyard with some M-B's and you'll probably find a nut for your antenna. You may also find some other odds and ends your car may need. Or, try places selling and installing car stereo systems.

Good Luck!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.