As mentioned above, Garmin are the most popular GPS in the US, I know. I had a Garmin and they have maps for everywhere you'd ever want to go, and places you won't want to go too. You may want to consider getting a radar detector as well. I'm not sure if you can upload NZ maps on it, but the GPS I had, I sold prior to coming here. There are a few huge retail stores that would sell them: Best Buys, Fry's Electronics, to name just a few. Fry's electronics is the best electronics store I have ever seen, in the world. You may want to look at their website. Their prices are stunningly low.
http://shop4.frys.com/
You'll have a blast, no doubt, as the place is huge and the roads are loooong. There are even places with no speed limits, due to their vast emptiness.
If you need any ideas, suggestion, information, feel free to pm me. I'm originally from Lost Angeles and have travelled all over the States... I can also hook you up with people there if you need anything, for accessories, dinner, etc., depending on where you are going.
Cheers....
Ride, eat, sleep, repeat!
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