Near the city there are ski / snowboard shops where you can rent your gear for multi day trips with the biggest being Snowride, Snow & Surf and Gnomes in Darfield. Methven has 2 established ski & snowboard rental shops - Big Al's and Alpine Sports. Near Roundhill and Oahu, there is a ski / snowboard rental shop In Fairlie,.
On mountain rental options depend on which ski field you are visiting. Mt Hutt has a large rental center designed to kit out people fast. They will even store your equipment overnight if you rent from them. Ohau and Roundhill also have equipment hire. You have less options at the smaller club fields if at all, so bringing your own gear is the way to go.