https://www.thingiverse.com/thing:3845007
I printed it out in some spare red transparent resin I don't have much use for since it's just a functional piece. I had to slim/trim the nubs that snap into the vent holes in the back of the printer with an X-Acto to make them fit, but that's pretty easy with resin.
The activated carbon is off Amazon - I just cut the square size I needed.