This tutorial will teach you how to make your own multi-layered juggling hat (like a Nils Pol) out of old felt hats you find in thrift stores. All you need to do is make a hat block with some insulating expandable foam, shop for some hats, fit them together and sew. Well... there's a little more to it than that, but that's what the video's for.
Link for buying unblocked felt hats online: http://hatsupply.com/woolfelts.htm