Not sure if this will help or not: I have 2 different gauges, one is actually part of a 5-in-one unit (air compressor, detachable lamp, voltage converter, jumper cables, etc.) and the other is a small, hand-held digital gauge that I purchased through Mid-America (or a like store) and keep handy in my center console.
The gauge in the 5-in-one unit is nice, but the unit itself is heavy/bulky and not something that you'd want to carry around in your car all the time. I pack mine if I'm planning an extended road trip where I think it may come in handy "just in case".
The digital hand-held guage is light weight and convenient. As long as you seat it on the stem correctly, I have found it to be just as accurate as the "regular" type gauges.