Use a bag such as this one to make your commute to work a bit easier. Maybe not a good choice if you prefer lots of colour choices, but it does come in black.
From OnBuy
Dicota Eco Slim Case BASE notebook case 35.8 cm (14.1") Black
BT Business Store
Dicota Eco Slim Case BASE 13-14.1"
This product is also available at 5 unverified stores.