Don’t bother with Endura Zyme’s, comfy enough but the pathetic button pops in a light breeze or the smallest movement. Before anyone else says it, it’s not the spare tyre causing it.
You can buy popper/press-stud kits and fit an additional popper which sorts this out nicely and will cost you a couple of quid for about 50 spare press-studs. Dead easy, you just need a hammer and a modicum of common sense… You shouldn’t have to do this, but you can.
I quite like my Zymes, though they’re a little warm in hot weather and heavy as hell when waterlogged.
Sugoi Gustovs for best, though they no longer makes them.