I hired a GS500 in Queenstown from this place >>
http://www.offroad.co.nz/rentals.html << Reasonable rates, VERY laid-back attitude, easy to deal with. Didnt seem too bothered about the offical paperwork. Not a very inspiring rental fleet though. But some fantastic riding roads around there to make it interesting. The road over the top from Queenstown to Wanaka is one not to miss