Aren't the carbon fiber B-pillars basically covers that stick on with double-sided tape? I bet you'd be able to find a factory-replacement piece pretty easily from ads where people part out their wrecked carrs or possibly a junk yard. I think a brand new piece from the factory would look a little funny since yours is probably somewhat faded and a new one would be all fresh and shiney... plus you'd probably save a few bucks buying one used.
Sorry to hear about your misfortune. Something like that would make me pretty upset until it was fixed.
07 WRX (Albins 5MT + Blouch 20G)
Jorge Carrillo Tuned (365 whp/340 wtq)