@emma
For some reason I don't see the post of Suiseiseki from this instance, in any case, here is my reply:
There are bug-poison evaporators that use standard-size rechargeable batteries so you can enjoy your bug poison while the other set is charging, some of them even have freelibre firmware… I think 🤔
The bug poison itself can remain proprietary or otherwise — there is usually nothing in there that you can't replace with readily-available ingredients — except proportions.