I bought a cheap sensor from Amazon. It seems to work okay. It roughly matched weather reports of air quality particulate when there was a wildfire near me. Though it can give some wildly wrong readings sometimes. For example.. I learned through experimenting that breathing on the sensor registers as Volatile Organic Chemicals (VOCs) and formaldehyde. Not sure that is right.

https://www.amazon.com/dp/B084N7ZRMJ/

Just note, YMMV when you buy cheap stuff on Amazon though.

Thank you u/lurdawg - I'll take a look! And have you heard anything about this one (I saw some positive reviews on it). https://www.amazon.com/BIAOLING-Accurate-Formaldehyde-Multifunctional-Recording/dp/B084N7ZRMJ?th=1