My husband is an Architect and we have a number of friends in the industry in NZ. I agree that the NZIA is a great place to start and get information about the profession in NZ. They also have a list of firms.
Unfortunately the architectural industry in NZ is small (we have a small population!) and it has also taken a hit with the global recession. There are still jobs out there but hard to come by, and often obtained through networking (knowing the right people, having relevant experience and a really awesome portfolio). Jobs are seldom advertised. My husband got his last two jobs through networking and "cold calling". Most recent graduates with a Master of Architecture (MArch) from NZ universities are struggling to find work. Initial employment contracts are often short term (3-6 months), salaries do not compare favourably with other professions with a similar amount of tertiary study, and unpaid overtime is common.
As construction tends to slow over the summer holiday period, many offices close for several weeks from Christmas onwards, and offices are often "wrapping up for the year" in December. This may or may not work in your favour if you are looking for people to speak with.
So sorry to say that it is not likely to be easy to walk into a job. However, meeting people face-to-face in NZ is a good start. You could also consider looking at ArchiCAD/Revit modelling jobs to try and get a "foot in the door" or completing some Architectural studies in NZ. Local knowledge and connections are invaluable.