Hi, the best CC deal by far has the be the Amex Air NZ platinum, for 1 year at least.

https://www.americanexpress.com/nz/content/airnz-credit-card/

Free domestic return flight, no card fee for first year, 200APD sign on bonus and usual other platinum perks. Essentially circa $400 for free.

Amex are rather good at retention offers, just ask. so may be able to keep going past one year.

I would combine it with Westpac airpoints platinum for those other merchants that don't accept Amex. Westpac has no first year fee also.

Cheers