As far as I know, you can ask for one at any Merc dealership.
But you have to be wiling to pay extra for it. But Merc will look after you regarding services and maintenance.
BIG BRUISER: Merc's latest Geländewagen sports a five-litre V8 motor and will go anywhere - but two snags. Only 12 are being imported this year and, well, they've not got the looks of the competition.