those kind of vacuum pieces are ubiquitous on most Mercedes cars of the era not specific to and model. Try a local salvage yard to see if you can find some. I just pulled a bunch of that kind of stuff of of a car in the yard to keep just in case.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"