If you have an idea of what you want, get in touch with my son as he makes cycle related bags, and may well be able to make you just what you are after.
My pal has a carradice super c handlebar bag which he likes . My dad has an ortlieb one the only problem he finds with it the bracket isn't very strong and doesn't grip the handlebar fully, the carradice clamps on , has a quick release and is made of waxed cotton so it sounds what your looking for .