Try a fire extinguisher supplier they can some times fix you up with an old CO2 cylinder and fill it for you or some one in the beer trade.
Hope this helps Pete.
Any ideas for a reliable source of plants Nelson area. I would like some Java fern/moss, echinodorus quadricostatus, E bleheri, Hygrophila difformis, Crypt crispatula var balansae, crypt wendtii, Aponogeton crispus, happy to have plants posted.
Thanks Pete.