I'm not the expert on this vintage MB (you're talking about the '82 300SD?), but the EPC shows only 1 trim piece across the bottom of the rear window pane, which it identifies as "Frame". P/N 126-678-14-30. That part apparently is still available and can be bought online for around $90-$95.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't