Over the years I have changed many brake pads on Mercedes models. I used to always buy them from the dealer. Apart from the MB star on the pads, they have the maker's name. It was always either Pagid, Textar or ATE.
I now buy them from Eurocarparts or GSF, making sure that it one of the three brands above. I know they may be a slightly different compound, but I have never had any problems.
(I ordered disks and pads today from GSF, they seemed a lot cheaper than Eurocarparts. In the past they was never much difference, but the gap appears to have widened)