You can purchase pre-programmed keys only from Jaguar. However you can purchase keys on the internet and match them to your car as follows:-
Jaguar X-Type Programming (Pairing) a Remote KeyFob
X-Type 2.0, 2.5 and 3.0L
Programming or pairing a new remote Keyfob for the X Type is a very simple job that will cost a substantial amount if it is done by Jaguar. It's annoying but this may need to be done if your Keyfob battery has been allowed to go flat, or the car battery has been removed for any length of time.
Follow these steps exactly and you should have no problems, pairing old or replacement Keyfobs for your car.
1.)I would recommended that you ensure all key fobs are fitted with new batteries. ( Click here
to see battery replacement guide).
2.)Get in the car and close the drivers side door.
3.)Put the key into the ignition and turn to position I.
4.)Wait 5 seconds
5.)Turn the key quickly to position II then back to I four times.
6.)You should hear a single chime.
7.)Remove the Key
8.)For each Keyfob in rapid succesion. Press any single button on the keyfob you wish to pair, you should hear a chime as each Keyfob is paired with the security system. After the chime do the next Keyfob.
9.)Check operation of each Keyfob.
Further info can be found on http://www.bluejag.co.uk