Hi there - I am a Kiwi Physio currently living in Australia. There is plenty of work in NZ which is easy to access as an Aussie due to the trans-tasman agreement. The hospital system pays in a similar manner (NZ dollars though) to your Australian loading, with similar perks. All these jobs are on 'seek' on the Physiotherapy Society website. I disagree with your ascertation that you earn less in NZ.... If you work private practice there is scope for much more money. In terms of locum agencies, at the bottom of the Physiotherapy Society / Association employments page, there is an area for locum opportunities. There are often a few locum agencies which advertise here as well. Alternatively, the other good site is the Private Practice Association (very cheap practising insurance) who have a number of agencies who organise locums etc as well as job advertisements. My husband and I locumed between businesses around the North Island, and though there is much work (especially in the lovely small communities) accomodation is expensive during summer months etc (when locums are required). Therefore an agency would be a great help if you could negotiate accomodation deals through them.
Hope this is not too confusing!
Good Luck!
ps. Beware of Private Practices who are ACC Accredited. These will tend to push you into treating way too many patients in very short time frames as they are payed per person. Make sure you iron out all the creases in your contract first!