Air Canada, United and Air New Zealand are offering cheap airfares to various Canadian destinations. These are the cheapest flights ever on Cheapies by around $70. Loads of different dates ranging to about August. Fares include bags, meals and seats. Most of these flights go through LA or San Francisco so might be able to arrange a stopover.
Find the cheap dates in Google Flights then plug them into Momondo.
Wellington $928 Google Flights
Christchurch $926 Google Flights