OP here. Searching around I came across this sort of PC case where you can put two ikea filters on the side and blow the air with 4 fans. (The Nukit Tempest Euro)
https://cybernightmarket.com/products/the-nukit-tempest-euro-pc-fan-air-purifier-kit
Price wise, $150 plus 4 fans would put me right at the limit of my budget, and I think it would filter less air than the classic 20 inch CR box, but getting ikea filters is cheaper and easier for me long term.
Opinions?