Help me choose/make a compression tester

[Infinitiguy19]

I am looking for a compression tester that has 1-2 PSI increments. All I seem to find is compression testers that show pressure in 5 PSI increments. Digital compression testers are overpriced and if they break they are trash. I am not sure they can be calibrated so that's why I say they are trash if they are off.

For those that don't know. A compression tester is just a tire pressure gauge with a check valve (And the proper hoses of course) with a 300 PSI read out (Gasoline Engine).