Why not do a Google search, have a look on EBay and ask your Citroen dealer?
All three activities should be within the grasp of an average user of the Internet.
In all three cases, it would be immeasurably helpful to know what bit you are trying to replace as "a small piece" isn't exactly much to go on. It may be good to know whether it would need painting if body coloured.
Not a psychic, May 2016
