From a FAQ on NZ Herald:
Will I still be able to online shop?
If you need something like a new board game or shoes, you might still be able to buy them online as long as the business is still able to operate with all its employees at home.
Couriers and NZ Post will continue to operate.
But it might be that many online stores aren't able to stay open so that might limit what you can buy.
You could always look for goods on sites like Facebook Marketplace and Trade Me, as long as the items are posted or are collected in a way so that you don't come into close proximity with the other person.