Hmmm, you C-class guys, do your cassettes go in "wide" way or "narrow" way? In my 190E, the array of 6 cassette drawers is 210mm wide by 55mm high, and the cassettes go in the "wide" way (that is, the exposed tape faces the front of the car as opposed to one of the sides).
If yours is the same then I'd bet I could use your same MB bin. But, I think yours may be the narrow way, and I'll have to stick with my homemade plan.
If anyone could measure and report their opening, that would be much appreciated.