I have to recommend FX Warehouse for nearly all your special effects and make-up needs.
I've been dealing with Thea, the owner, for a few years now, and she has always impressed me.
I have never had a problem with an order, and her customer service is fantastic! She is always helpful. Even if she doesn't sell the product you have a question about, she will do her best to help you out.

She has mask making, lifecasting, FX supplies of all kinds... How-to books and videos... Latex, both make-up and mask... Far too much to list!

Give FX Warehouse a look. http://www.fxwarehouse.info/