I got one from a scrappie, for £10.
Just had to strip the stuff out myself.
You need to find a Passat in around a 1995 vintage. Either take just the glass piece. Or if you've got the time take down the headling & remove the entire frame & motor. It'll all fit in a Corrado, although you don't strictly need the motor as your old one will work just fine.
Biggest gotcha's, be bloody carefull fitting as its easy to bend the sliding rails.
Get the runners & glass absolutly straight, otherwsie they'll foul on the roof. Thus the glass would scrath & break.
Insepect the sunroof seal, if it torn, worn or otherwise crap, you'll need to replace & this is a complete B**ch. Plus it'll cost £30 just for a seal. :evil: