Here are a couple of things I found to complete your Harry Potter theme
I found Hedwig's cage as a tea light holder at Michaels or a similar one at Amazon
(search for Bird cage tea light on google)
You can make Hedwig from polymer clay (for the body) and feathers or get a white owl from
e.g. Snowy Owl from Schleich or Snowy Owl from Bullyland
A trunk at Hobby Lobby, the web site says you can only buy it as a set but I was able to buy the smallest one in the store separately.
The chocolate frog card you can find in my blog, the frog I made from polymer clay .
The marauder's map you can find on my blog as well.