Hello, we'll be spending a day in Riga and have signed up for the walking tour. We still have a few hours before catching a bus to Vilnius. As the walking tour starts at St. Peter's Church, is there any supermarket nearby? Also, we'd like to buy some snacks for the 4 hours bus and I'd appreciate if someone can share some local snacks like chocolates, cookies, or anything unique to Riga :) TIA.