Have a look through the range of Scuba tanks and cylinders.
Scuba tanks or cylinders as they are known, are portable containers which hold compressed breathing air for use underwater. Most modern scuba tanks are now made from aluminum or steel and are capable of holding pressures as high as 3000 psi or 200-300 bar.
They consist of a valve which controls the flow of air and a Burst Disk which is a safety device which discharges air from the tank if too much pressure builds up.
When buying a tank the buoyancy, capacity, size and how often you are going to be using it will have to be considered. it is also wise to have your tank serviced annually regardless.
Protective meshes are also a good idea and they come in many colours.