IGN maps; 1:100,000 for the Le Puy route:
50 - St-Etienne, Le Puy-en-Velay
58 - Rodez, Mende
57 - Cahors, Montauban
56 - (just a corner; you do not really need it)
63 - Tarbe, Auch
69 - Pau, Bayonne
They are 6 to 9 Euro in bookstores and tobacco shops in France. Usually you can only get the local one and maybe a couple that connect to it, so you purchase them progressively as you walk.
They are excellent for finding alternative routes when the weather is bad or when the official route is not the most direct route and you are pressed for time.