Here's a $3 gauge.  It doesn't have convenient vias to solder to, but the LCD pads are large enough that it may be possible to solder to then and not interfere with the relatively thin LCD connector piece.  Of course, the LCD can be dispensed with entirely, and if a visual output is needed, a small OLED screen could be fitted.  I tend to not need the screen on these, the data are most useful transmitted to me or to other nodes, from their remote location.

This particular gauge has a separated on/off switch - the white thing at the bottom of the board. That is a plus. The other gauge had its activation switch internal to the pressure chamber, and would activate upon inrush of pressurized air.  The timing of this was monitored by the gauge's microcontroller, so doing it manually via ATMega digital pin meant some experimentation with the code.  Here it is decoupled.