I’m trying to find a reputable vendor for an accurate 0-1000ppm CO2 sensor for some experimental monitoring. Of course Chinese vendors make me a bit nervous, but if you have experience with a vendor who makes a good sensor I’d love to heart about them.
Thanks
I am looking for the same and spoke with an expert in interior climate regulation. He said that its easy to make a cheap co2 sensor, but its going to drift very much, and needs calibration at least once a day. Normally the outside air, which has a known co2%, is good for calibration. He says there is many sensor-manufacturers working on a cheap and reliable co2 sensor, but he is still waiting. Let us know if you find anything… 
Given it’s outside air we are measuring for a CO2 climate change experiment accuracy and consistency is hugely important. There are lots of shiny CO2 sensors, but finding a reputable manufacturer who makes a sensor at the level we need has proven to be surprisingly difficult which in itself is very interesting given the emphasis which everyone has placed upon CO2 and climate change.