There may be some Brugge only places, but of the traditional Belgian chocolatiers that have a presence in Brugge, my choice would pretty much be Mary Chocolatier. In Brugge at Katelijnestraat 21, 8000 Brugge, Belgium. It's one you're not likely to find outside of Belgium (never have; may not have looked hard enough). Their chocolate is pretty amazing.
When I'd travel to Brussels for business, I'd buy Leonidas for the office; I bought Mary to bring home...