Sounds like a pressurized system, cheap at 80quid to. No experience of it first hand, but email Richard he's very knowledgeable and is always happy to help
I would say get a refillable cylinder thought, it'll probably work out cheaper in the long run, that's if you can find a place to refil it, which can prove difficult. That said, you can get very cheap disposable CO2 cylinders on ebay, 3 for 15quid if I remember rightly.
I'm suprised that people have problems getting their CO2 cylinders refilled. I can get it done for £10 at my local Maidenhead Aquatics. It does take a week though and they can't guarantee an empty for full swap. That's for a 500g JBL cylinder.