Kind of ridiculous design. I know the e53 had a separate PCV that could be replaced easily and cheaply. No aftermarket valve covers that I'm aware of, nor would I really trust one. Those go through a lot of heating and cooling cycles, and a crack is no good.

I know I came across a posting somewhere where somebody was selling a kit to repair the PCV valve. Super cheap, but required breaking the plastic welding apart and prying it open...then replacing the diaphram....then gluing it back together. Probably like $30. No idea on the success rate on that one.