Have you tried…
Kōhunga Kōrero

Bilingual books in Te Reo and English
Wellington City Libraries have lots to choose from. Here’s just a small taster:
Kuwi & friends Māori picture dictionary / Merewether, Katherine Q.
“From the #1 bestselling and award-winning author and illustrator of the Kuwi the Kiwi series, Kat Merewether, comes a large scale, stunningly illustrated visual dictionary. Full of over 1000 basic words in te reo Maori and English, perfect for every New Zealander.” (Catalogue)