Some years ago my aunt had sewn a vest that a zipper that converted it into an actual bag. Even when in the vest configuration, it was double, so it essentially was one single big pocket. You could stuff tons of things inside, and given that you could convert it into a bag it was also relatively convenient. You would keep it as a vest when having to prove that you would't carry other bags than allowed, and back to a bag at all other times (including during the security check).