There's a Franprix at 11 RUE DU CHAMP DE MARS, which is about 2~3 blocks southeast of the eiffel tower (about 2 blks east of the middle of the champ de mars park, cross av de la bourdonnais, then av bosquet).

There's also a Monoprix at 2 rue du commerce in the 15th, which is toward the metro stop La Motte Picquet Grenelle, about 5~6 blks away.