Take bus 6 (or others) four stops from Pile Gate to the stop in front of the Tommy store. Just opposite the door into Tommy is Bio&Bio. Buy bus ticket in advance at ticket office at Pile Gate stop for 12kn, which is good for all travel within one hour. It's a one-way street, so when finished at the shop, cross street, walk around through the gas station and cross street to bus stop heading back to Pile.
Shop has a good array of products, a few frozen items, a refrigerated section, packaged grains, etc. Jars, bottles, snack bars, corn chips, rice cakes, juice, alternative milks. I bought some nice hummus made with pumpkin oil.
This store seems to be unique in Dubrovnik. Let's support it!