Conad is a great solution in Italy with a large and cheap selection. In Rome, Milan, and Venice they're less conveniently located (Via Buonarroti is probably the best location in Rome, unless you're near EUR), but in Bologna and Florence especially they're easy to walk to from the center. You can find locations beforehand here: http://www.conad.it/conad/it/home/puntivendita.html. Have a good trip!