For $20 you can get this tire inflator that has a built-in digital pressure gauge

$20

GOOLOO (99% positive lifetime feedback) via Amazon offers its Digital Tire Pressure Gauge and Inflator for $19.79 Prime shipped when you use the code HMEHU8FE at checkout. Regularly $30, this is one of the best prices we’ve tracked historically and is the lowest available. If you’ve ever had to use a manual tire pressure gauge, they can sometimes be hard to read or inaccurate. You’ll be able to read up to 255 PSI with this digital gauge and it’ll also function as an inflator if you plug it into an air compressor. Rated 4.3/5 stars.

If you don’t need the inflator portion, check out this digital tire pressure gauge for $9 Prime shipped.

GOOLOO Digital Tire Pressure Gauge & Inflator features:

• [Wide Range and High Accurate] – Performance tested & certified accurate to ±1% with display resolution of 0.1 for maximum accuracy; Features four kinds of measurement ranges: 0 ~ 255 PSI, 0 ~ 18 Bar, 0 ~ 18 Kg/cm2, 0 ~ 1800 kpa.
• [3 in 1 Multifunction Auto Tools] – A Tire Inflator + A Digital Tire Pressure Monitor + Tire Pressure Releaser, heavy duty solid construction, gauge dial head is guarded by thick rubber protector, huge lock-on air chuck
• [Leakproof Lock-on Air Chuck] – Heavy-duty leakproof brass construction Air chuck perfect avoids air leaking and ensure accurate reading for you!
• [Easy to Read] – 360 degree rotatable air hose for easy reading, Backlit LED display with four measurement options: PSI, BAP, KPA, and Kg/cm²
• [Battery Saving and Warranty] – Auto shut off after 15 seconds of inactivity to preserve battery life. Protective rubber covered gauge for extra shock protection. Built-in air bleeder valve to quickly decrease pressure in overinflated tires. Our fan-favorite 18-month warranty & 30-day money back guarantee and friendly customer service.