Does anyone know where I can buy snowboard boots that don't have any leather or other animal materials? It would have to be somewhere online or a store in NZ

I wish I had a more specific recommendation for you. My best advice is to call or write the popular manufacturers (e.g. Burton).

You can go to a closeout site such as this for a deal, and then write the manufacturer about the models you like:
[www.sierrasnowboard.com]

Good luck and let us know what you find.

The snowboard boot brand "32" Thirty Two's boots are usually all synthetic! Check em out at www.thirtytwo.com