Clearance item (not many in stock) for $54 at MSY Slacks Creek. Pick up only I think (not sure). Some in stock at time of posting. Probably best to reserve online.
PQI H567V 640GB White External USB3.0 Hard Disk Drive. Cheaper than a 500GB USB2.0 drive.
http://www.msy.com.au/product.jsp?productId=7425.