[gsich]

MH-Z14 or Z19. But this is just the sensor, you'll need an Arduino/ESP/Rpi too.

[AYBABTME]

What's particular about these sensors? I've been researching technologies to monitor plant growth and haven't yet looked into CO2 sensors, hence my asking. Do they come in an IC package?

[gsich]

They use optical measurement, are reasonable in pricing. Outputs are UART, PWM and analoge.

They have pins with 2.54mm spacing if that helps you.

[AYBABTME]

Would you use something else if you meant to solder something on a PCB for medium scale production?

[gsich]

Don't know. There are chemical sensor with a heating element, but those usually suck.