Well, I basically took the tester and removed the battery spacers out that were obsolete
Due to the size of the battery which was slightly smaller by a 5th of it. I then took an old Phone usb and usb adapter charger and clipped the micro usb connection off exposing the internal wires I then soldered the negative to negative and positive to positive and ran several test to confirm if is usefulness it worked like a charm.
tested the tester by plugging it into the outlet and computers even my car and it worked :)
so here you go enjoy
a Fedtro Vacuum tube tester circa 1966
To USB Conversion.