Shipping from US to Euro is approximately $50 for a standard keyboard.
Soarer's conversion uses the Teensy ($20, + small envelope shipped from Washington state) and converts the controller to a mini-USB-B plug. You have to do a little minor soldering, but it works well.
I have not done one on an XT, but you should be able to fabricate an outboard box if you have a female DIN connector.
On my projects, I mounted everything inside the case, but the XT has less room and an outboard box is more versatile.