https://odorhog.com/
•Filters can also install onto vents that are directly connected to the septic tank
In your case the vents are on the leach field "downstream from the tank" but I assume these would work for that as well. The only thing you'd really need to understand is if a filter such as this would significantly restrict the free flow of air as these vents are put into the field in strategic locations to allow ample air flow in the field to help dissipate gases that build up in the drain\distribution pipes.
Talking to a septic designer, ideally the one who did your system may help answer if this is a viable solution. Smell emitting from those vent pipes is not uncommon after all they are installed for a reason.