The naval peacoat is flattering, handsome, and is suitable for both casual situations and going out. It’s heavy but not stifling, even if you live in California like I do, and it pairs exceptionally well with a sweater if you’re looking to survive even the coldest temperatures. It’s also classier, more durable and less expensive than the many, many fashion imitators.
If your local Army-Navy store doesn’t sell real vintage, you can always try Ebay or an online vendor like the one I cribbed the above photo from. You can get a pea coat in great condition for $50 or $100. Go with Vietnam-era or before, when the construction was at its best. And remember that they are sized with the presumption you’re wearing a bulky sweater underneath. If you don’t plan on wearing a sweater, size down 2-4 inches from your normal chest size. I bought my WWII coat, a size 38L at a garage sale in high school. Back then, 38 was more or less my chest size. It still fits me fine today, with a 42" chest.