Nova fire services / Pressure Check Cylinder Services I think is one place, just checked and it is in Grey Lynn. (09) 378 9243 give them a call first as I'm not 100% sure they do fills (but 99% sure they said $11 for a 3.5kg fill). Your cylinder will have to be within its hydrotest date for them to fill it (if not they can do the test for you, but it is a bit of money)