Toy shop are called "la grande recrée" " king jouet" "jouetclub" they are some toy's rus too.
Yes you can very easily finds G4 ponies in the following places:
"king jouet" "la grande récrée" "jouet club" "toys' r us" which are toys shop
but you can also find in supermarket or hypermarkets such as:
"Auchan", "Leclerc", "Carrefour", "Intermarché"
and of course in spring, summer and autumn we have plenty fleamarket where you can find some old toys (not always G1 but sometimes yes ;o) )
Good trip in France, hope you will enjoy ;o) and good pony Hunt ;o)))
Good hunt