The Asus EeePC 1101HA did not ship with a protective bag so I had to buy one separately. Naturally you don't want your laptop to roll around in your backpack without any extra protection at all. It turned out to be a bit tricky as this laptop is 11.6" in diameter. All the bags in the market seemed to be have been designed either for larger or for smaller laptops!
After visiting about three other stores I finally wandered into Clas Ohlson and found what I was looking for: a neoprene sleeve, for less than 15 €. The brand name is "Aldata". It says in the case that it is designed for 10" laptops but I found that it still fits the EeePC 1101HA perfectly. It is also nice to be able to use the laptop without actually removing it from the sleeve, as there are two zippers going around it. The sleeve also contains handles that may be left outside the sleeve for carrying the laptop around when inside a building or for short distances anyway.