Dictionary
Astoria always liked to have a dictionary nearby where she was. With her reading a lot now she always liked to grab her dictionary if she ran into a word she didn't recognize. Instead of using a big dictionary and hulling it all the way to Hogwarts, Astoria bought a pocket dictionary; she could carry it around when she went someplace.
When Astoria was in a muggle store in America she found a little pile of the pocket dictionaries. With that she was delighted. Without passing it up she bought one and kept it with her always since that day.