The idea of investing in a piece tells me you'd like to have this piece for a while, and you should—it's a classic, masculine piece that will always be in style. Thus buying a modern, single-breasted option would be counterproductive to the overcoat's storied history. I'd suggest the British label's updated "Trench 19 Slim," a shorter jacket with higher arm holes for a more narrow fit while retaining the coat's classic proportions. After all, if you're buying Burberry, the trench will likely outlive you. And don't worry about being a fair-weather wearer. A non-slicker raincoat is the perfect cover when the air gets chilly.
Slim-cut trench, $950 at Burberry.
In 1880, Thomas Burberry invented gabardine and in 1914 was commissioned by the British military to create the trench coat.