Hi,
You've probably found that none of the aftermarket suppliers carries this item. Allpartsexpress does or used to, special order under the following part numbers 123 295 03 40, 123 295 03 50, 460 295 01 13- contact them. I believe the last number is the hose itself, the other two may be brackets, which you probably don't need. As mentioned above, you can replace the tube with a generic piece of brake line from any auto supplier, but there are many types of fittings - take your master or slave cylinder with you when you go to buy it, so you can match it up. Also remember that Mercedes uses the "bubble" type flare, which crushes into a double flare when tightened, you'll see what I mean when you look at the tubes. US cars use a single flare. Getting a generic hose is another story; you will find that the parts stores only catalog by application, i.e. make and model. If you go to the NAPA website you will find a list of brake/clutch hoses with length and fitting type called out. Once you figure out what fitting you need, you can pick out your hose and get it at your local NAPA store. I went thru this myself and ended up cobbling a hose together from some fittings and brazing the whole thing together, looks awful, but it works.

For the life of me, I don't know why this hose is not commonly available.