my local Morrisons had loads of these good quality cases in the offers section.
The Kensington SP10 is a classic notebook computer sleeve for when you're on the move. This 15.4" sleeve protects your notebook with a durable nylon exterior that's tough enough to travel with you. Plus, interior and exterior storage compartments have plenty of room for important files and accessories.
Kensington SP10 15.4" Classic Sleeve - Notebook carrying case - 15.4" - black