Here are images of MGA Judson gauges and gauge faces.  To get a basic gauge, buy a modern one and then build it into an older housing using the face images here.  To get the dial finger, buy a Marsh gauge on ebay - if you get lucky you will even get a gauge that is fundamentally the same as a Judson gauge, but is missing the Judson script.  I have managed to do this a couple of times.  Otherwise buy a repro here (warning, not safe for your wallet).