The X10/X20 is a rangefinder-styled camera; as such, you're always going to see some lens in the VF in the lower end of the zoom range. This is just the nature of the beast. Those of us who've used rangefinders just 'get used to it'. This is why Fujifilm copied the 'slotted' lens hood style for the X's: It helps you see thru it.
You can use the Fuji or the aftermarket copies which adapts the native 40mm front thread up to a 52mm filter size. Everyone makes filters in 52mm, so whether you prefer Hoya or Tiffen or B+W, whoever, you're in business.
With any of those adpaters, the problem some of us have run across is they are vented as well, so you can wind up with dust on the inside of the filter or the lens' front element. This requires removing it usually to clear this out, and since the lens hood screws into a slightly bigger set of threads around that, you have to take the whole thing apart to do this.
That got old for me quick. So I purchased a Marumi Digital Clear in 40mm from 2Filter.com (No, I have no relationship with them, they are one of the very few places that offer these). It screws directly into the lens, and then the adaptor/lens hood screws into that, and I much prefer that arrangement. Marumi also makes a 40mm polarizer, but no ND's I'm afraid. The Marumis are very reasonably priced, and the quality seems fine, and 2Filter is great to deal with in my experience.
