If you are flying into France, and then traveling by train to Le Puy, I recommend bringing the items already packed, but not sealed - in case some official is nosy.
Once you arrive in France, seek the first La Poste office near where you are. You can do this online., There is likely an app. IIRC La Poste even has offices in major airports.
Post the parcel to an accommodation you have pre-booked in Le Puy or SJPdP. Ask them BEFOREHAND if you can send a (describe box size) to them to hold for your arrival. I usually call them replenishment supplies.
I have always had success having an item shipped ahead to a hotel or hostal where I have a reservation. Even if your dates change, if you notify the place you booked and where the parcel is headed, they will certainly hold it for you.
In Spain, the Correos has an excellent Camino support system of various sized boxes, inexpensive shipping and storage at the destination.
Hope this helps.
Tom