PLEASE read all of this, I know I'm always harping on safety. We have had a few injuries reported in the forum by honest caring individuals. High pressure air is dangerous to life and limb, To get the performance of a shop compressor like 10 or 20 cfm at 90 psi takes about a 5hp motor and often a 2 stage compressor . Sealing large pistons well enough to be able to hold 4500 psi is difficult at best. 4500 psi requires a lot of power, cooling, and high quality steel to build a 4500psi compressor to be able to preform like a cheap Chinese $100 shop compressor. The shoe box pistons are about 1/8 for 1st stage and smaller for the 2nd stage (boosting psi to 4500). I think the motor on my shoe box is 1/2 horsepower and has a reduction pulley system to allow the motor to handle the load. I'm sure someone somewhere makes a large piston compressor for 5000 psi, It would probably be dangerous to fill gun tanks with, to quick and dangerous to stop from over filling. A large tank would be necessary to fill 1st, they are not cheap, plus a valve and gauge and hose all rated for more than 4500 psi. The compressor would have to be extreme tough and require a large gear reduction and high horse power motor in order to with stand the heat and stress on the compressor generated by compressing air to 4500 psi. It would not be easily transported due to weight etc. The amount of force to compress air to 4500 psi is very large so the smaller pistons, higher grade everything - seals. pistons. cylinders etc are necessary to generate high pressures. Till the demand of pcp air guns came along no one engineered a small compressor to do the job. Look at scuba compressors, most are only 3000psi. The industry has come up with " hobby" compressors for air gunners cause there is a demand and people to generate enough sales to make a profit. Price, weight, size, safety, dictate these compressors. Just remember people have been killed by 300psi steam leaks so small they can't be seen or heard because high pressure steam is invisible, there is no water vapor in it and pin hole leaks don't make noise they just cut off body parts so fast it doesn't give the body time to hurt till it's to late. They look for them with straw brooms waved in front of the person. When the straw was suddenly cut off the broom they found the vicinity of the leak. Pin hole leaks in high pressure air systems are serious. My father demonstrated what a high pressure leak is capable of with the straw broom. Buy quality! Buy safety and be safe and always vent fill lines before uncoupling your fitting from the gun or tank. Our hobby is relatively safe. There is a potential for injury, more so then owning, storing and using live ammunition and fire arms. I have always been impressed with Joe Brancato and his air tanks, micro bore hoses, gauges, valves, fittings, Regulators, fill valves designed to not fill to fast, adaptors and hose assemblies.He is an engineer who knows if it a paint ball air system component or one safe enough for our use. He has expanded his business to air rifles and accessories. Buy good gauges look closely at them and remember the pressure you read so you can tell if there is a leak, listen, if you are concerned use a sheet of newspaper or note book paper and slowly use it to check for a high pressure leak. We used to carry .22 ammo and larger calibers in our pockets, my father learned it in WWII when ammo was more important then water. We don't carry live ammo like that anymore.
If one of these $100 LPA systems were the magical fix we'd have jumped all over it now. The mid-grade compressor market is heavily focused on. Maybe try one of those $250 Hatsan Spark clones?