Pretty much anywhere around Halloween but any other time i'd try a Halloween store.
Harry Potter costumes can be found on eBay and Amazon and also at various online stores such as Buy Harry Potter Costumes, Wholesale Costume Club, and Costume Craze.
You can buy them a set of books in a display case or a Harry Potter costume.
The price range for Harry Potter costumes vary. It depends or where you are looking to buy a Harry Potter costume. You could do a search for Harry Potter costumes to find the best price.
at book stores...
book stores
You can get stuff from a bunch of places like book stores like chapters or indigo would sell books sticker books and other Harry potter related books they would also sell bookmarks and like best buy or future shop would sell the DVDs Harry potter Lego could be found at most toy stores and if ur lucky u might be able to find Harry potter stuff at other stores
Amazon is an option. There are others, too. Most book stores will have it.
You can buy it in all good toy shops, argos or type in Harry Potter Scene It on Google and you can buy it online! x I have tried almost all stores online, and no luck. I just tried argos and still no luck. Any other stores that you have seen with this game in stock?
You can buy it online like off of Amazon.com or in stores that sell DVDs also
I would try a store that only sells candy and has things that are not sold in many stores.
Party City and Amazon both carry Harry Potter costumes at reasonable prices. I have dealt with both stores in the past and was pleased with their products and shipping.
There are plenty of Riddle Costume for all ages that you can buy at many halloween costume stores.