I checked with one of the local MB dealerships the other week. He did some kind of search and said that there was one in the whole country still in inventory. If I remember correctly, it was about $350 or so. I didn't purchase because he couldn't show me a picture and also couldn't confirm if it fit a 300E or a 300CE, (I got the CE). The stated maximum weight that the rack can carry is only 200 pounds. That makes sense as the only mounting points are the drip rails. Plenty enough capacity for bicycles or kayaks.

Try doing a search of the archives. It has been discussed before. Someone modified a Thule rack to fit. The bolt size is either 8mm or 10mm. Best place to get bolts is a marine supply store. You will get good quality stuff that the weather won't affect much, (i.e. probably won't rust). All one would need is a standoff of a few inches with rubber gromets to protect the anodized rails.

Good luck in your quest. If I ever modify something to fit, will document and post experiences. Proabably won't happen as my Ranger pickup is still running well.