Post this in the "Car Audio" forum and see if Scott of "LaJolla Car Audio" will reply. He is very knowledgeable about MB installs and head units in general and even repairs OEM head units.

He might be able to procure one for your model...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car