Do you mean the stud for the downpipe? I believe the studs for the uppipe are installed on the uppipe not the turbo..
Either way, you could use a stud extractor to remove the broken stud from the hole, then just tap a new stud into place. Inexpensive fix. I also have a stock turbo from my 02 WRX, but I'd probably want more for it than it's really worth.
[EDIT]Never mind.. I see what you're saying, the flange on the turbine housing broke[EDIT]