I contacted my Citroen Dealer (CITROEN MOTORHOUSE COLEFORD). A budget 19inch equialent will cost around £120 with tyre. I think the wheel is a 16 inch with a deep profile tyre fitted to make up to 19 inch. Haven't purchased one yet as I thought I will run with the reair kit for now! Try your dealer and see what they come up with for you.
Regards,
MOJ