The corner marker or the turn signal on the side by the gills?
In any case, just google "BMW Z3 side marker light" or "BMW Z3 side turn signal" and see what pops up. I'm sure you can find one from one of the site sponsors.
I think you are saying that it plugs into the socket that holds the bulb. That socket is apparently shown on the back of the signal in the photos in Post #6. But that socket does not look like it is shaped to receive the plug on your "piece". So I am confused about what your piece is, and why it should be between the turn signal's bulb socket and the car's harness.
And why in your Post #1 do you say that "piece" is bad?
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