Do you have a Fry's Electronics near you? I know there are tons of those stores in California, dont know about anywhere else. I know that Fry's almost always has the Hori brand screen protectors in stock.
Go to a blockbuster with a game rush. They always have extras and you might be lucky enough to find someone willing to help you out. They might even give em to you for free, who knows. They usually end up tossing them in the trash.