For years, I have carried an Eagle Creek briefcase with integral pack straps. I can wear it like a backpack, lug it like a briefcase, or simply sling it by one strap over my shoulder. In the field, I have used it as a chest pack while wearing a larger conventional back pack. Mine is at least twenty years old and is still presentable enough for office use. Similar models remain in the Eagle Creek line, and I am sure similar rigs are available from other sources.