timbuktu…
I use my old timbuktu “rockshox” branded courier bag, which has been indestructible for the last 16 years! I ripped the padded section out of the bag work supplied me with, and just bosh my laptop in that and then in the courier bag. Seems waterproof enough for all but an extreme shower, in which case I chuck it in a carrierbag first. Biggest problem I’ve found with it is that it’s black inside, and you don’t end up spotting that old banana for a few weeks…
Oh, and Howies had some grim coloured ones for cheap in their sale last time I looked. Still the same bag tho.