It has to be pressed out and pressed in to the new blipper.

You can't as far as I know. You need a special code, that is delivered on
a card (creditcard size). The computer in the Car has to be re-programmed
with a new code and the blipper and all spare keys have to be re-programmed.
If you don't repogram the spare keys, than you can't start the car.

The Citroen garage can do this job for you, they can also request a new
code from Citroen-France, if you don't have the card or lost it.
If you have the card, than try to find a store that sells keys, locks, etc
and
duplicates keys. Some companies have advanced equipment to re-program
and duplicate keys. Usually this will not be a small tools shop at the
corner
that also duplicates keys.

Good luck!