I bought a co2meter.com model RAD-0301 ~6 years ago that was probably the cheapest prebuilt NDIR unit at the time. It just shows CO2 ppm and temperature. It lo

I bought a co2meter.com model RAD-0301 ~6 years ago that was probably the cheapest prebuilt NDIR unit at the time. It just shows CO2 ppm and temperature. It looks like they've slightly improved the features and dropped the cost more on their followup model https://www.co2meter.com/products/co2mini-indoor-air-quality-monitor https://www.co2meter.com/products/co2mini-indoor-air-quality... this is not going to be lab grade accurate but if it works as well as their old one it's great for the price and fits your requirement.