You can also do fills using scuba tanks as a booster. I go to a field that uses a smaller gas powered compressor and uses the tanks to give the 4500 psi boost.
The compressors that fill to 4500 psi are several thousand dollars though. And while you don't have to be certified, you should be knowledgeable in servicing them like oil changes, air filters, etc.
Dragon/Russian Legion/Ripper 3/Species/Vice Intimidators
Mirror's Edge/ Darq 7 / Red Edge
Silent Hill Cyborg
geI t my SCBA 4500psi 87cu.ft. Carbon-fiber tanks filled for 5.00 each at local scuba shop and use them with
the Rocket Booster to fill my paintball tanks to 4500psi (as the scuba shop can only provide 4000psi fills)