Simple: pick up an old AC unit or refrigerator, (less capacity), cut all piping/tubing and hook up to an gas cylinder.
Flush that one first to get the gas out!!
Install a filter on the suction.
Install a relief valve set to 8 barg (120 PSI) to protect the cylinder.
If you want to do it real nice, built in a pressure switch to stop the compressor at say 100 PSI.
If you install the cylinder upside down (so connection on the bottom) you can add a drain valve in the filling line to get rid of condensate.
These compressors are pretty good, can reach pressures of over 20 Barg (280 PSI) if dead ended, so a relief valve is required.
TakeCare

PS: I would go for air powered wrenches, much safer
EDIT: the set-up will very probably violate your local pressure vessel code so dont sell them.

 

Sorry I can't post pictures on this anti-mac site, I've pm'd some I just took, feel free to post them if you have the ability to.