i just got back from a year in new zealand (what a coincidence!) and i have found that if you don't flash it around, and its not like a otf switchblade or somthing nobody really cares. i don't know the laws exactly but the people there are real people: rough and uncouth. they'd understand if you had a (reasonable) knife.
i carried a CRKT M-16 12Z knife that i could flick out and a buck revolution xt. the crkt was probably illegal but someone only mentionde it to me once and it was one of those passing comments (I'm suprised they let you into the country with that.) nobody cared about the buck
another thing: filet and fishing knives are very common. everybody has one in thier ute or van. but you don't carry a filet knife, do you?
good luck and have fun