As of 1st October 2015 our old work around to get a proof address by getting an IRD number has got a lot harder. IRD now require you to get a bank account first.
So if you are serious about getting a proof of address you will need to establish a bank account. This may be easier from overseas as you can use your overseas residential address as part of the verification (as you will not have proof of address in NZ as yet).
Here are some links to different banks in NZ (in no particular order) -
We would recommend the kiwi bank one as we know they have a bank account ("free up") that doesn't have account fee's.
When researching for this article I also found a nice post on Trip Advisor about banking in NZ.
Once this is done you can get the IRD number application form here -
Questions? Please add a comment below.