I’m looking for a small footprint gas analyzer to use in my mammalian cell culture to measure carbon dioxide. Any suggestions?

I would take a look at the products offered by the folks at BlueSens, specifically their BlueInOne Cell. It is a compact gas analyzer capable of measuring in parallel both carbon dioxide and oxygen online as well as in real-time. They are a German firm with a rather long history of addressing bioprocessing applications specifically. Here is the link to more information;

BlueInOne Cell