something from the movies signed by the cast
if you mean the 7th horcrux, well it was harry Potter hope this helps
Hufflepuff's Cup.
In Quidditch the Seeker seeks the Golden Snitch.
Harry Potter was looking for information on Nicolas Flamel because he was connected to the item being guarded by Fluffy. Harry and his friends thought the item was going to be stolen and wanted to know why.The item was the philosopher's stone which was made by Flamel, a friend of Albus Dumbledore's.
If you are speaking of the snake for a potion in Lego Harry Potter 1-4, there are a number of potions that have this item as an ingredient. Let us know where the cauldron for this potion is, and we can tell you where to get the snake.
A Broom is used as a sports item in Quidditch. All players use it.
An item called the ressurection stone - see the tales of beedle bard
teddy bear
A woven blanket.
You can find a detailed description on how to find each item using the link below. http://www.gamefaqs.com/ps2/561368-harry-potter-and-the-chamber-of-secrets/faqs/20858
Shopping online would be the easiest place to find a Harry Potter costume in case your local costume store does not carry this item. www.costumeexpress.com and www.costumecraze.com/index-harry.html are just two of many places you can find one.
Just to name a few of them: Invisibility Cloak, Marauders Map, Resurrection Stone, Elder Wand