I’m not an RT but what about something like this that’s cheap?

https://www.amazon.com/Digital-Tracking-Software-Accurate-Reliable-Spirometer/dp/B09S3KJZZ7

Or the MIR SmartOne Spirometer which I use. But it’sa like more expensive at $130

https://www.amazon.com/MIR-Smart-Personal-Pocket-Spirometer/dp/B07LGZ64KB

The EasyOne would be best but looked it up and looks to be around $2000.

Maybe some RTs can give their take on the cheap Amazon spirometers