I haven't worn a bumbag (as the Brits call it) in the traditional way in ages, although I have sported one across the body "messenger style", which I remember first seeing in the pages of Fruits. This etsy shop has made me think of those unflattering, bulky little things differently now. Edward de Lacy's leather belt bags have an imperfect finish which I think could contrast quite nice against a more "perfectly" tailored skirt or pant.
Each belt bag has a unique shape, which in the case of Etsy's more personal connection with vendors, could probably be customized to your liking. They come in white, brown, and black and go for $50 a pop!