One inside a crate/box on the floor on the left side of the shop.
Two are on the counter on the right side of the shop.
One is inside a broken metal cabinet at the back of the shop. It is partly hidden behind a broom, which you may need to move in order to pick up the lunchbox.
One is inside the locked desk at the back of the shop. You need a Lockpick skill of 50 to open the desk without a key. There are two keys to the desk, one in a nearby toolbox, and one in a cash register.