National Championship Winners
This well maintained Wikipedia Page records every New Zealand Championship winner (New Zealand champion). Winners of other important New Zealand national championships are also listed, including the NZ Rapid Championship, Major Open, Premier Reserve (archaic), Women's Championship, North and South Island Championships, and Correspondence Championship. There's interesting ancillary information such as multiple NZ Championship winners and double (Championship and Rapid) winners.
A PDF snapshot of the Wikipedia page is available here, as a backup of sorts. The current snapshot was made after the Wikipedia page was updated to reflect the 127th Congress in 2020.