I've found that Pelican Parts has one of the better selections of molded cranckcase breather hoses for the Crossfire/M-B cars. Go to Pelican Parts and search using a 2004 Model Year Mercedez-Benz, then select the SLK series. Click on the SLK32 AMG. Once you're in, go to Engine / Oil Circulation / Cranskcase Ventilation. The only hose shown looks like the one you're looking for. (See attached file)

All the other molded hoses typically needed are listed under the SLK320.