As for the space, this bag has a volume of 18 litres. If you prefer brown bags, then this should you just fine.
From Amazon
Fjallraven 23524-243 Kånken Laptop 15" Sports backpack Unisex Terracotta Brown Size One Size
The product is available from £92.29 at international stores.
This product is also available at 1 unverified merchant.