Stud: N 000835 006082, at Mercedes ca EUR 2. It is a generic part.
Bracket: A 127 070 20 24 at Mercedes, ca EUR 220 (consumer price), EUR 130 at SLS or Niemoeller.
Note: the nuts there are special, coned, A 127 990 01 51, at Mercedes EUR 3, SLS EUR 3,6, Niemoeller EUR 5,37.
I am sure the SL Shop would have those parts as well.
I would try to drill the broken piece on the table drill to screw in extractor.