I agree with Paul -- a do-it-yourself redye is pretty easy. I did mine a couple years ago for the same problem.
The other source for dye is colorplus.com .. THey have a nice web site and lots of useful info on auto leather upholstery in a free brochure they'll send you. You can also get small lots of their dyes.
The other advantage to colorplus is they have MB official colors (like gray, palamino, etc.) in stock so no custom mixing charges. I redyed my driver's seat and it's a perfect match (gray).