clothing hunt

So I was on Lainey's site this morning, and saw this picture of Jennifer Garner. I'm in love with that sweater. Love that it's got the Army/Sargent jacket style details, but it's a cozy zip up sweater. Awesome combo. How do you go about finding out what brand it is or where she got it? There must be celebrity or fashion sites dedicated to that kind of thing... I just don't know any.
Anyone seen a site like that, or a similar sweater? Help me!