You can still buy them from Mercedes. These items are sought after due to the inherent corrosion issues. The thing is when I have come across good second items over the years (particularly for SEC's) they were often within 10% of a new item.
Get a part number for it and do some searches, you might find it new for half sensible money. You will also probably require the two small joint cover pieces. These have the studs attached and will be corroded to a degree that's likely you'll have to cut them off.