You can buy a bearing with two rows of balls but this isn't one you need to use. This type of bearing is for high speed applications. The correct one is a spherical or barrel roller bearing designed for load. Since your rear axle shaft probably won't turn faster than 1,500 RPM's at any given time, this is going to be the correct bearing.
I have no problem getting this bearing which is special order through my regular supplier. It costs more than a standard bearing because it has a very specific use that isn't commonly asked for. MB would be the last place I'd go for something like this, but since I haven't, I guess it would be fair to ask what they want for this part.