What other activity involves sitting around, mainly motionless, for hours and often in the cold months or into the early night? But with the chance, at a moment's notice, of having to be mobile and active?
CARP FISHING!
So if I were seeking out a garment for a high seat I'd look on a carp fishing forum or seek an internet review of an angler's "all-in-one" or "bib n'brace".
I use my trout boat fishing "bib n'brace" by a company called Vision for pigeon hide sitting. It is green, warm, waterproof and you don't sweat inside. But maybe not quite "man" enough for really severe cold weather sitting though! OK for autumn weather or winter day time but maybe not if frosty.