CARRADICE CARRADICE SUPER C RACKBAG

The Super C Rackbag is made to the same exacting standards as the other members of the Super C family. There are no zips to get caught or broken so this bag can keep going for years and years. It will give you a similar capacity as a saddlebag whilst fitting on the top of a pannier rack for a streamlined position.
https://www.carradice.co.uk/bags/rack-packs-stuff-sacks/super-c-rackbag