Any 240 volt three stage or dual motor 2 stage unit rated for 5.000 to 8,000 square feet. I have no idea what is available in N.Z. Plan for a minimum of wall inlets for bets efficiency. An unfiltered cyclonic is nice, if you can install it in a garage or exhaust it into the courtyard or from another exterior wall. Ours is a Vacuflo 466Q, and it does not exhaust any noticeable dust into the garage from the muffler end. It's very strong, and rated to 5,000 sq. ft. but it's 120 volts @13 amps. The 566Q is for up to 8,000. They make a dual motor, and at least a couple 240 volt units, bagged as well, and filtered cyclonic bagless ones.
I do believe that the pcb boards and 24 volt transformers are all rated to 240 volts, so I don't see why a 120 volt unit can't use 2220-240 V. It would also draw fewer amps with 220-240 v.