I only find all the time a complete fabric USB Hub with 4 ports or more.
What's the problem with them? You can close the case of the two additional ports or fill them with hot glue if you really don't want them to be available.
can I use 2 Host USB shield using a rewiring of the SS pin to communicate with the Arduino Uno?
Yes, you can but you have to almost completely rewrite the software for it. Don't think of this to be an easy task, you have to have some in-depth knowledge of the USB bus protocol as well as of the used chip set. Sure you have the library for the one shield version but you may get some serious problems extending that for a second shield (as felis already told you).