As I understand it the 350GTs CVT is a unique design, not at all like the one in the Maxima or Presage or other VQ35DE Nissans (this is why I went for a 300GT with the 5 speed)
An entire car can be had from $12-13k NZD (which is a fair bit weaker than the Aussie at the moment), even if you had to buy the whole car and have the transmission removed and shipped it might be an option. You could sell the rest on to a wrecker or for maximum money have someone part the car out for you (I know I'd pay good money for the part-leather seats and the rest has got to be worth something). Obviously the problem here is its a logistical nightmare you don't know how much life the new box has in it.
Edit: The CVT guy in NZ may have access to a few wrecked/parted out cars which could explain things. Best to tread warily though.