I bought Germ Guardian Air Purifier during the pandemic for 140$ and is about a year old.
https://www.amazon.com/gp/product/B01CTN024Y/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

As I'm leaving the Bay Area for graduate school, I can sell it for 50, if you can pickup from Mountain View. I can also deliver it to Stanford for a small extra fee.