Several places sell them, but if I remember right when I was looking into it, they are not activated until you actually turn the telephone on in Brazil, so they may not work unless you find somebody who is going to activate them for you.

I believe all they have to do is connect there and they will work after that.

If all you need is a phone number in Brazil, consider places like

http://www.tollfreeforwarding.com

where for $10 a month you get a local number there (though probably not in the cell blocks of numbes), and 112 minutes of forwarding back to the US. Test what you need to test, then cancel it. Depending on how much you need it, that may be considerably less then buying a very overpriced sim here.