You can pick up these, Mini 2.5V-30V 0.28" Display LED Digital Voltmeter Voltage Tester Meters, for about £1 each.
But I needed to give the connectors a more secure holding, and I wanted to be able to mount them on a board.
I used some self tapper screws I had lying around, they are not critical, as long as they fit. Connector block was the smallest I could find.

A variation on this here
https://www.thingiverse.com/thing:3718400