It's already been mentioned, but I would buy it on a credit card and balance transfer to Westpac/ANZ who both are running 12 months/0% promotions.

Failing that, approach your NZ bank and get a secured loan.

DO NOT get a loan from the car dealer.  They are not your friend and they will rip you off something chronic (I have inlaws that love doing this, and I bang my head against the wall when we discuss who this isn't such a good idea)