If you want to DIY these there's a FOSS (GPLv3) parametric builder web app that will output files for 3D printing, lasercutting, or handcut foamcore and calcula

If you want to DIY these there's a FOSS (GPLv3) parametric builder web app that will output files for 3D printing, lasercutting, or handcut foamcore and calculate the performance of different configurations for you: https://www.filterboxbuilder.com https://www.filterboxbuilder.com There's no real performance difference between DIY and metal PC fan filter boxes, just durability.