I think they are a bonded tailgate. If so you will need a tow ball mounted one, Thule are very good as are Witter, but neither are cheap.
Hollywood do a 3 bike carrier that you can get foam covererd dumbells for which fit to the end of the mounting straps and sit inside the tailgate allieviating the strain as they pull on the metal inner not the glass or the bonded tailgate.
ive got a standered halfords hatchback cycle carrier,with fittings like chris m describes.i got it for my mondeo a few yrs back and is still going strong now,and yes it fitted on my 2002 scenic.
got it cheap from halfolds web offers,its worth a look