is a polystyrene ball covered with cold porcelain, paper feathers and painted with golden paint
to see the step by step here is the link http://www.instructables.com/id/Cold-porcelain-Golden-Snitch-step-by-step/

PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format.
You also have the ability to customize your PDF download.
you can find cold porcelain y art stores or stores of handcraft materials, but if there's no possibility to find one, I let you the recipe to make it
http://www.youtube.com/watch?v=svwW74M00hU&feature=related
and some tips to work with it :D
http://i-be-c.deviantart.com/journal/FAQ-Cold-Porcelain-Clay-238544772