Looking at Al's link, a couple possibilities come to mind for those who like to "re-purpose" things. First is an older stainless steel fire extinguisher. They are pumped up to 120#. Second, is a small beer keg. They accept tri-clamps and seal up well with the right gasket.
Pete, pressurized engine pre-oilers like this one will work if you fab something for the muzzle end. -Al
https://www.jegs.com/i/JEGS/555/23550/10002/-1