You sure can! All retailers should be upgrading your empty 30L gas cylinder for a full 60L cylinder for the price of a refill. Check out or store locator to find authorised retailers near you - https://www.sodastream.co.nz/pages/authorised-retailers.
To swap your blue screw-system cylinder for a pink Quick Connect cylinder please visit a Briscoes, Harvey Norman, Noel Leeming, Farmers or JB Hi-Fi.