My wifes old C200 has these trims, think it enhances the look of the car, but was told by local MB last year, that these parts were no longer available, but I did see a used set on Ebay very recently, so there must be a chance of picking some up, given time. It may be possible some of the independant mercedes parts suppliers may have these, (euromerc, starpartz etc ) it may be worth a phone call, albeit it may help to have the part no. to aid your cause, and keep an eye on Ebay.
I priced up a set of these late last year and they are available still, but not as a set, you have to order each one individually, and IIRC £56 each!! so over £200 for a complete set. If you would like the pt. no.'s I can post them for you, but you will have to wait till I get home.
The set on E-bay recently was incomplete, it was 3 separate auctions, 1 trim per auction.
They had an option code, and was a modification to vehicles with AMG rims, though not all vehicles with AMG rims had it as it was only nessaccary in certain European countries I believe.