Yeah, there aren't many places to buy mac games in NZ but there are some. Totallymac.com probably has one of the widest ranges and they are online. You local mac shop like magnummac probably has a few but you would likely have to go in to see which ones. Trade me has some older games sometimes but you don't get to choose which ones come up.
If you want a particular game I would suggest calling a local shop and see if they can import it for you. It won't be cheap though. Mac games are more expensive generally, and because of US laws you often can't buy them direct from overseas so you have to pay for importing in the price. unless you know someone travelling to the US.
All this is why I stick to older games

Good luck..