Over the years of working in some hellish poor areas in the world, I found there was little substitute for DEET.
Mozzies etc in places like West Africa, India, Malaysia and South America to name a few didn’t like it at all.
I used to bulk buy the good old “Shoo”, once manufactured in Argyll. This was always the best I could find hands down.
It was quite aggressive to plastic however, as some of my salmon flylines and reel handles will testify but it was effective nonetheless.
Incidentally, I recently worked with the grandson of the man whose original idea for “Shoo” came from and he who told me that Canada is where it is now produced. Probably why it’s difficult to get these days??
Anyway, I have now moved onto “Lifesystems” Expedition Plus in 50+ for skin and 100+ for impregnating mozzie nets etc and find the 50+ isn’t too harsh and a decent compromise. Doesn’t sting the eyes when sweating but if you use synthetic stocks then I’d test a little spot just to be sure!
LIFESYSTEMS Bite Relief
You could always try the old tip getting hold of some Bog Myrtle if it grows in your area, rip it out the ground, mash up the plant in your hands and rub that on, a very good natural repellent which really does the trick for the Scottish midge.
Be warned though, don’t digest it, apparently it’s a hallucinogenic so god knows what you’d see peaking through the scope
It’s an ongoing battle for the holy grail of a decent non-aggressive repellent, some swear by Skin so Soft but I find you need loads of it regularly applied to be effective and you do smell like a "hoors handbag"
Good luck in your search.
Rigboot