I got Alaska from fishpond.co.nz, after searching for it for forever :P
I can't find any in Whitcoulls or Borders but went to Unity books in Wellington the other day and found Looking for Alaska.
Trawl the bookstores too! I found a SIGNED copy of Will Grayson, Will Grayson in the bargain bins and the Albany Borders for $5.
Best of luck to you! Dftba :)
Right now TFiOS is cheap on amazon, like 8 bucks, i havent found any john Green books either although most libraries have a couple.