Looking for a concentrated liquid in bulk to hook up to hose to spray outdoors.

can only find supplies for mosquitos and flies and discovered, after much $$$, that these do not work.
any ideas?

Anything you spray outside that kills gnats is going to kill a lot more than gnats. Is that worth it given their relatively short season? IMO, no, but if that's what you need to do, any general insecticide will work to varying degrees.

Thanks. Actually talked to the pharmacist who recommended (and sold) a bottle of Absorbine JR. didn’t know that was still made. They keep it behind the counter.

I can’t do bug repellant, sunscreen or suntan lotion, or permethrin.

When I really feel bothered by them, raising your hand draws them away from your head at least. They always go to the top for some reason. I know that is not what you were looking for in an answer but figured I would mention it.

12 gauge with skeet loads...
A little over kill but ..........

On a more serious note I've heard fabric softner sheets pinned to your caps works....

I know a garden-person who said she rubs a light coating of plain mineral oil on the whole outside and under the brim of a hard hat. The full brim style works best. The gnats bump into the oil and stick there. Not exactly canoeing fashion, but it works in a yard/garden setting. She never mentioned color preference.
I've sprayed pyrethrin on my Tilley hat (especially under the brim) with good results. Gnats and mosquitoes stay a few inches away.