A couple years ago I bought a nice brass dial gauge by Accu-Gage.
I got it locally for about $15 but it's also available from Accu-Gage's web site.
Accu-Gage site
I selected the gauge because they actually stated a specification of accuracy:
"A 60 psi tire gauge is accurate to +/- 1.2 psi from 15 to 45 psi and is calibrated to ± 1 psi at 30 psi. " They make it in other psi versions also.
Quoting from their site"
"All Accu-Gage® 1-1/2", 2" and 2-1/2" dial tire gauges are ANSI Commerical Grade B gauges, which is the best quality gauge typically used for tire pressure applications.
These tire gauges use a fully geared, solid brass precision movement with bronze bourdon tube. Unlike piston-plunger-type gauges, the bourdon tube movement is not affected by changes in temperature, humidity, altitude or air stream contaminants.
The mechanical accuracy rating is ± 2% from 25% to 75% of scale and ± 3% below 25% and above 75%. "