RJ100 2crew min 1575psi, 3 crew min 1100psi.
But I'm not sure why psi is important. If made the storage container half the volume, the psi would double , or double the size of the tank and halve the psi, and you'd still have the same amount of O2.
The regulator in the system will reduce it to a pressure that you can breathe.
I don't know what quanitity of O2 tht pressure equates to, but our manual sayas that for a/c certified to fly at altitudes greater than 25000', in the event of a pressurisation failure, there must be suficient O2 for the entire flight, subject to a minimum of 2hrs.