Where can I buy cheap sled things near Christchurch?

Hi! Australian family heading to the south island in 3 weeks for a motorhome road trip. We are west aussie so snow is a huge novelty for us. Wondering where I can buy some cheap snow sled thingoes for my teenagers when we arrive. Thank you 😊 Also do you guys have op shops because I think we will also need more blankets and some kitchen items 🥰