Yeah, I know, all the parts stores have them. But they all have a 300 pound scale. It would be nice to have one for low compression engines.
I might suggest you buy a compression tester for a modern engine. Select a model where you can remove the gage and replace it with a low pressure gage, 100 PSI, from a water system. These gages can be found at good hardware stores. With that approach you will have the benefits of the low pressure check valve and the spark plug hole adapter, etc that a purpose made pressure gage has.
The easiest way is to find a lower reading gauge on the internet and put it on your tester.
I bought a 0-60 gauge from eBay. It's about 6 inches wide which makes it very easy to read when yer long in the tooth!
Garnet