The 1900D I use isn't fantastic, but it has an Air NZ paint. It was designed for FS2002 but it's ok with FS9 (don't know about FS X).
It is of unknown origin and has no readme, but download it
here.
I have the Francisco Sanchez-Castaner ATR which is okay, but the ISDT one might be better.
Search for his name on Avsim and you should find it. I have the Air NZ textures
here.
I don't know about a good Q300, but
Premier Aircraft Design makes one that I think has an Air NZ paint (if not, one could be made). I have no idea if it's any good.
For the others I'll second Project Opensky - they really are good, high quality aircraft. Their recently released 777 is excellent

.
I have ARNZ's Baby Boeings which I think are pretty good, but the consensus is that Vistaliners is the best 737 classic.