I have used a service called Price USA, they are based in Australia, however, they freight to NZ as well. They charge a 5% service fee and service has been good each time. Have a look at their website if interested.
I used Shipito and they have worked flawlessly. If you compare the price of shipping a Nokia N900 today to NZ from Amazon using Shipito.com and a Nokia N900 purchased off PriceUSA.com you can see who wins...
N900 Handset - $825.86 Shipping to Shipito - Free Shipito Fee - Flatrate - $11.70 Shipping to NZ - $48.49 Total - $886.05 NZD
N900 Handset - $834.21 Shipping to NZ - $49.42 PriceUSA Fee - 8% - $70.69 Total - $954.32 NZD
Shipito also has more options for shipping, doing your own customs declaration and you get a mailbox in California which you can use multiple times.