I took a hitch off a 123 300d at the pick and pull. It was universal hitch simply bolted to the bottom of the bumper. It looked like it had seen quite a bit of use and I could not detect any damage to the bumper. For a trailer as light as yours, I'd give a hitch like that a try.
I spent the summer camping in France. Everyone pulls trailers with their Mercedes over there, including fairly large caravans. If you do an 'all country' Mercedes hitch search on Ebay, you'll find a hitch designed for your car much cheaper in Germany or the UK.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13