Well there's ABS which is much tougher than PLA but still not tough enough to make a complete mouthpiece from. There's nylon but that's just a bit more flexible and not particularly heat proof. My buddy has some carbon fibre filament coming but I still doubt it'll stand 200C+. Most hotends can only go up to about 230C; although some of the newer all metal hotends like the E3D can go up to about 320C. Basically everyone is working away like mad to produce a hotend which can do 450C+ which is hot enough to be able to print aluminium.
I think at the moment printing a replacement mouthpiece is just not possible but give it a year or two and I think it'll be worth revisiting.
BT-01 Update:
I tried creating a more streamlined version but I came across two problems. 1. Making the design so it fits snugly but is still easy to remove is a lot harder when you try and refine the shape. 2. I'm not very good with sketchup yet; which probably explains problem 1.
So, for the moment I have kept the square design but I have reduced the inner wall of the top face so that the water tool can be fitted more snugly onto the P/GOnG.
Final version of the BT-01
Fitted to the PnP
+ Water Tool
Obligatory Sideways Test
I wasn't sure if the little holes than run across the side of the device where air holes or not so I made sure they were not covered when the shroud was fitted in place
/End show & tell
I will keep playing with sketchup and do a BT-02 version which will be more streamlined but for the moment this version works fantastically and blends in very well when done in black.
I will be uploading the file to thingiverse in a bit so if anyone wants to have a go at printing it or remixing it while I get up to speed on Sketchup then feel free.
I am not adverse to putting a little FC logo on the side of this if it is something people might want.
EDIT: Download the STL from Thingiverse Here