Carradice bag, yes it’s big but I took a few extra layers today plus a huge Belgian bun to go with the coffee!
https://www.carradice.co.uk/bags/saddle-packs-sqr-bags/carradura-maxi-saddlepack
https://www.carradice.co.uk/bags/saddle-packs-sqr-bags/carradura-maxi-saddlepack