If you have a youshop account and don't mind paying $37.50nzd for shipping to NZ then you can get a $50USD code from an Nvidia employee on the https://forums.geforce.com forums. This is through the Nvidia Shield Store.

See this thread
https://forums.geforce.com/default/topic/892328/shield-android-tv/amazon-offering-50-coupons-for-nvidia-shield-tv-/

Sign up to Gefore Forums and ask ManuelGuzman for the code. It is 1:30pm in the US at the moment and the code expires on the 5th November in the US so hurry.

This is for the $199 Nvidia Shield TV, with the code now $149USD
Or the $299 Nvidia Shield TV Pro, with the code now $249USD

By my calculations that is still a $37NZD discount on the product landed. The Amazon code people are talking about is single use and no one seems to have any.