Some SC history on the subject
By law in France license plates must be fitted by rivets. You may not wish to buy the tool needed for rare use, so the garage may be a better choice.
You can order your own plates online
We used (a few years) ago we changed our plates using an approved garagiste to order + fit
https://www.norauto.fr/plaque-immatriculation.html
https://www.norauto.fr/rechercher/plaques%20immatriculation%20plaques%20et%20pose
Booked the time, carried our plates to them and all sorted in 15 minutes. (Not only do they fit the new plates but they also remove the old ones and hand them to you as a keepsake 
)