If you are in So Cal you might fine one in a Pick n Pull you can cut off a 108 or even a 111 4dr-they are the same. Mine was rusty too and I cut a rust free one off a donor car and drilled the spot welds out and grafted it on. My car spent most of it's life in San Francisco where it's damp and by the ocean so it got a bit of rust.

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Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT