I don't know how good they are with men's clothes but the Opportunity Shop at the National Cathedral might have some nice stuff as its in a wealthier area, though if I had to guess, I'd assume there's more women's stuff there, but I really don't know.

If you' wear a size 17ish, a customer at my job gave me some white button down shirts around that size. You are welcome to them if they fit you. He offered and I took them, but I am only going to keep maybe one of 5 as I don't really need any more button down shirts so I'm happy to give them to someone else.