I may be able to source some Huawei E169 USB modems which will work on Vodafone NZ to give you 3G over a pretty good chunk of urban AND rural NZ, with the footprint currently expanding rapidly.
They should be available in 2 - 4 weeks and probably cost around $400. They will be Huawei branded and with the addition of the Vodafone APN to their software utility should work fine. I will of course be testing one here in NZ before I commit to buying one.
Let me know if you are interested, stock will be limited.