Some of them do read well, and "some" may be very good.
Even the failed mrodair compressor the factory ( originally) advertised filling only small - in the cc range NOT tanks) bottles & tubes directly on rifle with a run time of a few minutes. That mrodair unit might ( not likely due to QC) have worked for brief fillings of say 13ci tanks? To me ( with NO engineering ability) it seems it it wouldn't take all that much to build a compressor made to fill an airgun - 200/300cc or even 500cc. FX hooked there gen2 hand pump up to a motor for fill airguns ( NOT large scuba/scba tanks) and I do know of one that still runs.
I believe most U.S. ( esp. ) airgun folks do not want to fill there rifle once then shoot & re-fill rifle from pump. Most want to fill large , 80cf & up , tanks for many fast refills.
But depending on a persons true "needs" IF you can find the good manufacturer of one of these SMALL cylinder compressors, then it might be worth the money to some.
Now such a unit with NO support in your Country, "I" wouldn't purchase one. "I" certainly would like to see some legitimate dealer with parts & service carry some such device though. I do think there is some market for a tiny high psi compressor but less so all the time.
I went with the Altros Booster, $614 and works perfectly even filling scba tanks.
John