I have no connection to this company from Czechia, just happy to see that Fly Henry are still going strong and improving their designs. They make very affordable, simple EMS instruments for two- or four-stroke engines.
https://www.flyhenry.cz/index.php/en/products/fly-meter-eng
https://www.flyhenry.cz/index.php/en/products/ppg-meter-eng
https://www.flyhenry.cz/index.php/en/products/fly-meter-eng
https://www.flyhenry.cz/index.php/en/products/ppg-meter-eng