Cartridge for fire extinguishers

[Corazones]

I am overhauling my CO2-water fire extinguishers which I "inherited" from a retail business I used to run, and which I now use at home. The service engineer at that time showed me how to inspect the container for signs of corrosion, how to remove and check-weigh the CO2 cartridge etc. The problem is it's difficult or impossible to obtain the cartridges, type BS5423. I've tried a security shop that sells extinguishers but they will only service them (at an extortionate cost), not offer parts. It all sounds very much like a "closed shop". Any ideas, please, how and where I can get the gas? I had heard that it is also used in beer making - is it a standard "keg beer" type as used in a pub, does anyone know?
Alec

 

[breezer]

as you said its a cartridge, the idea is when the pin is struck it pierces a lead seal, releasing the CO2, once pierced cartridge is useless. you need a new cartridge.

try a fire extinguisher company