Hi,
This is a good period to come to France now as some of the flea markets are beginning (thanks Spring
) They are mainly hold during the weekend.
During the week, your friend can try to go to an Emmaüs shop, it is a social shop where you can find everything and sometimes kids plays like ponies. I personally never went in there because I have no Emmaüs near home , but some collecting friends have already found nice items there.
Good luck to your friend and a wonderful trip in France