Found that the herb dryer has a typical kitchen exhaust carbon filter.
There's many shapes, circular included to fit the fan. They cost way less. Instead of 20-25€ we get it for 5-8€ but you got to change it every 3 months...just like herb dryer description says about theirs... For this project this saves money but also space since it's way shorter than odorsok filters. I can add 2 of these ( one for each compartiment) and still be cheaper.