Once again, http://www.precisionauto.com sells them for nearly all of the SLs including 94+ models that have the Bose system. Cost is around $1350 for the textured vinyl and $1600 for the leather. They even come with seat belts (I guess to give the appearance that an actual person can even SIT back there).

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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