The FreeBiz 50-liter backpack is less than 50 euros on Cdiscount. The bag has a padded pocket, ideal for laptops up to 18.4 inches.
An adjustable strap keeps the computer in place, to avoid unwanted shocks. On the side of the bag, on the outside, an extendable mesh pouch allows you to store a water bottle or umbrella. To protect your bag from water, a cover is hidden in a small pocket, under the bag. Finally, the padded shoulder straps are comfortable, and you also enjoy a clip-on chest strap.