if you're having trouble sourcing and you don't mind, you can bojang one on the cheap
this is essentially what one is. you can add charcoal filter for smells, etc in addition to HEPA. personally i prefer a tunnel fan that can suck/push air in a direction vs a regular box fan but i know someone that did this and seems to work for them.
*edit*
my fav is the top comment about a lab coat and wall of books so you know it's legit
