I don't believe they exist. Probably because they'd cut your tongue and the facing of any plastic/rubber mouthpieces wouldn't last too long against them and metal only slightly longer. I personally wouldn't want to go through mouthpieces like they were reeds.
theres this guy that makes a titanium reed setup, 189 dollars, but close to no information is availiable on them on the web, and hes hard to find. The thing is, the setup is one thing, can't put the reed on a different m/p