When I bought my S1 there were no door keys and only one of the push button door lock barrels. The other lock was missing as were both plastic trim rings around the push buttons. They were initially sourced from Renault, most probably from the R16.
I ended up buying the following parts from a Renault online shop in the Netherlands:
Plastic trim rings, Renault part 7700537758:
https://www.renault16shop.com/7700537758Set of three locks with two keys for the three locks:
https://www.renault16shop.com/Webwinkel-Product-155326179/The keys came in Renault style what I quite like. Installation was simple, but I will need to glue the plastic trim ring into place.