I go to Vic and it's got around 10-20 people who do it or are going to do it next year. As for Waikato, no idea.
Posting in the Australia forums isn't going to help answer your question however...I'm only look around in here monthly or so. Also, very few NZ cosplayers post here.
Alex (Golden Sun) - 70% (Arbitrarily assisting you, sort of.)
and his Djinn - 40%
Desires for the distant future