Timpsons reckon that they can make them for Citroens but I have yet to try them
The "key" comprises two items.
First, the fob contains a transmitter/receiver that activates the central locking and alarm systems. I'm fairly sure a used one can be dialled in to your car by anyone with a Lexia or Diagbox software.
Second, the key assembly also contains a small black transponder chip. This is essential to the car actually starting. If you purchase a new key it needs to have this chip or it will only unlock the car and crank it over - it won't actually start. The transponder chip is paired to the car with Lexia or Diagbox; it's quick and simple but you do need your four-character access code as supplied on a plastic card by your dealer.
So, hunting around sundry Pug/Cit forums including this should reveal a person close enough who's got the correct diagnostic kit and will work for a fair price. No need to pay a dealer unless you really want to.