Amazon.com: NPT 1/4" Pressure Gauge, Dual Scale Mechanical Manometer for Water Air Oil Dial Instrument Base Entry 0-7bar 0-100psi : Industrial & Scientific
Amazon.com: MEANLIN MEASURE 0-5psi Diaphragm Type Capsule Low Pressure Gauge 1/4" NPT 2-1/4" FACE DIAL Adjustable Water Column Gauge, with 1/4" x 1/2" NPT and 1/4" x 3/8" NPT Hex Bushing, Lower