Yes. Search for CO meter on Amazon, many of which are portable enough to be placed in a backpack. I used to have one, but its battery leaked which damaged it. These days there are disposable lithium batteries and also models with a built-in rechargeable battery. There are also some that measure both CO and CO2, and it's good to measure both. An example is B0CRQZNPLV.

Note that some these meters can alarm, and sometimes alarms can be false, so if you don't want one that alarms, then find that one.

Note that there is nothing much that one can do while in flight except take pictures, videos, complain loudly, change seats from back to front, threaten to sue, maybe use the oxygen mask if lucky, and take down information of other passengers, all before fainting.