Clay, I started out with a BOC gas bottle. They cost a lot - $130 a year rental plus $37 a refill from memory.
Thankfully, Doogiechap put me onto the extinguishers from John at Eversafe mentioned above. He's a very nice bloke and even dropped my bottle off to me in Freo as he is on the road a lot. It cost $175 for the extinguisher which comes full. I'd go for that as I haven't seen anything near that price. If you have an old extinguisher, he can modify it too. The top of the bottle, threads etc match those of any BOC bottle and so will take any CO2 regulator.
The only worry with an extinguisher I think is the cost of re-fills. About 6 months ago I had a leak in a new set-up and ran out of gas. I rang around everywhere and the few I could find were charging over $50!
Rang John and he put me onto the mob he uses in Catalano Circuit (near the corner of Catalano Road - big factory) in Canning Vale. I can't remember their name (something like Australian Safety/Fire Solutions) but Doogie might have it buried in an old email I'm hoping as I couldn't find them in the phone book just then and you do need their number.*
They charge $22 :icon_cheers:
So if you deal with John (9493 2044) make a note of the refill mob as the catch is, *you need to ring them before driving out there to make sure that they are doing a run of CO2 refills. If you don't ring, you'll end up having to leave your bottle there for their next run.
Spot,
Pat