You probably already know this, but the Corrado was never sold in Australia. In fact, the Scirocco has never been sold in Australia either. So any you see are all private imports.
Mark Hammond brought his VR6 Corrado to this years' VW Nationals in Sydney. Beautiful car! I believe he was interested in selling it; unfortunately i don't have his contact details but someone here might.
You could also try ringing Matt at Camden GTI in Sydney - his Mk2 Scirocco is in the latest issue of VWMA. If there are any Corrados coming up for sale, he will know about them. 0423 051 737
http://www.camdengti.com.au/