It depends what year you want. Last years are easy to get cheap. I've seen them for about $600 NZ in Wanaka Good Sport and i've heard there were some for $300 (all NZ$) at a shop in Dunedin (But it was closing down). 
Outside sports Qtown stock them, so does good sports in Wanaka, small planet Qtown, Racers Edge Wanaka. IF you want this years i'd say you'll probably have a hard time getting them cheaper than $900 NZ