It's a T25 saftey torx bit, you should be able to get it at a local auto parts store. I bought a whole set at harbor frieght tools.
i got mine at sears http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00925702000
Hell, as many times as this question has been asked you'd think Ford would put it in the owners manual! U.M.
Advanced auto sells the security torx bits in a kit for about $8 and it gives you about 5 differents sizes