Inflatable Object Pressure
for a design class, we came up with an inflatable object and need some help with our ideas. the object must maintain pressure. what are all the practical options out there? it needs to be compact and lightweight, pressure must be maintained around 3.5~4.5psi, and be able to relieve pressure if it gets above 4.5psi (due to elevation, temperature, etc). we came up with air compressor, pump, manual inflation (by mouth) and was hoping to see if anyone has any other ideas. any help is appreciated.