I've bought this Nokia case, and it's a perfect match for my X10 Mini. Even the color, as I have my Mini with the green back.
The main compartment opens from the back, wich add security, and the Mini slide in and it's the exact size of the plastic window in the front. And yes, the touch screen can be operated trough the plastic (I do it with my bike gloves on!).
On the back of the case, in the middle of two "bumps", a pocket for a key.
And it has a opening for the headset wire.
I use it to carry my Mini on my Mountain bike tours, for music and gps, and it is perfect.
Link to Nokia product page.