I'm using a Musto bag at the moment.
Good size. Comfortable to carry.
Side pockets for drink bottle and flask. Couple of zipped pockets on the front and the lid good spectacles etc
Waterproof and looks good without being too "tactical" or at the other end of the scale too satchel like.
Musto as you may know is a brand based in England. The brand was established in 1965 by Keith Musto, a British Olympic sailor and engineer.