Mercedes offers them, though I don't believe any that say AMG. I picked one up from the dealer. It has the Logo on the front in the same place as the one on the car, and even a extra piece for where the antenna is. Though I pulled a little too hard one day and ripped a hole in it. I believe I have the dust cover, as it's always in the garage, I think it was around $400. I think they also make a regular cover for around $200 with UV protection and such.
I just received my cover yesterday. I ordered a Noah by Covercraft. Very nice, well made, and the fit is very good as well. No, it doesn't have any logos on it but if I ever cover my car outside, I wouldn't want anyone to know what it is. There are some pretty mean and jealous people out there. Price for the cover was $200 including storage bag, cable lock and shipping.