Which link was that? The OE one from NC?Well, so much for ordering the sill covers from that link. NLA. That site seems to list a lot more than they can get.
The SL shop in UK has them it seems and probably the SLS linked above too. Seems they may be reproductions.
Millers say they have them: https://shop.millermbz.com/rubber/rubber_door_sill_mat/68_3550
Authentic Classics too (Genuine MB) - 2-piece sets. https://www.authenticclassics.com/SearchResults.asp?Search=1076860180
MB Classic may be another option. Their Euro site shows some as being available still, probably just certain colors.
Mercedes-Benz Classic Ersatzteile