Just for example. Not sure how up to date it is (I think 2015)
If you buy a kilogram for 39 CHF then maybe you could cut it and sub sell it as an ant killer mixed with the honey and other ingredients mentioned before.
I also saw some old children's Chemistry sets where you can make "Slime" which uses Borax as the main ingredient.
Where there is a will there is a way - I am sure a friendly Chemist could easily get hold of this stuff. (for experimental reasons) - It is not really that dangerous.
I remember when I lived in Asia, there was a product called Nippon (probably spelt wrong) which seemed to have a similar effect - you dripped it on the ants and they carried it back to their colony and it destroyed the nest. (was a long time ago) - maybe this was also Borax?
EDIT
Just found a link for Nippon - it is not Borax it is Spinosad
Try and find a welding shop nearby. It is used as a flux in many metallurgical processes.
I just used Terpentinersatz in our paving stones. It worked pretty well. I guess you could mix ant poison in with it, but plain terps worked fine for me.
We are having a severe problem with ants in our kitchen. We are on the ground floor, so we are the closest source of food indoors for them. I am spending about 45 minutes every day with extra cleaning and having no results. I have also added 8 ant baiting stations in the kitchen, with little results. I told me reggie about the problem and asked for the building to be treated (There are only 6 units) as I cannot treat anything outside my unit. They have so far done nothing to help. Any thoughts on what to do next?
We keep a pretty tidy home (Plus, wife is Suisse ) but we had the same issue a month or so ago, nothing was working (Natural routes, i.e. non-toxic). I succumbed to impatience and sprayed and nothing since
I was pretty impressed at one point, they are relentless and tough
I had issues with ants in my 3rd floor apt, luckily bedrooms not kitchen. Tried all the Swiss stuff for yonks, did nothing. Last summer I was in UK, got some borax based ant powder. Boom.
Migro Optimum (yellow plastic spray with red and white nozzle head, picture of ants and other creepy-crawlies on the label) is the only thing I've found here that works.
It's a barrier spray so you'll need to find where the little feckers are gaining access and spray across the doorway, window sill, etc. .... but it also works pretty well if you just zap 'em 'on the hoof'.
If it's any help to you, I wrote a post about this linking to a test of the products currently readily available in Switzerland. I strongly recommend Oecoplan's ant traps from Coop. We had an overnight result with no return of the little blighters so far.