Stylish, clued-up men are looking beyond Patagonia and going gaga for a new wave of hiking-style clothes. They’re good-looking—and, often, pricey. Call it Gorpcore 2.0.

The trench’s fundamental appeal, though, extends far beyond its utility. There’s a reason it’s favored by everyone from Wall Street tycoons to Camden Town punks, to say nothing of the mood board ...