Zombie Hunter/Level 5

First quarter
A shop at the beginning sells Medicine x2, Medicine x4, and Thunder Lv5.

Second quarter
Above Battle #13 is a hidden shop which sells Medicine x1, Medicine x3, and Armor Lv1.

Third quarter
Above Battle #20 is a hidden shop which sells Medicine x2, Medicine x6, and Mace Lv6.

Fourth quarter
At the left of tiny platform of Battle #25, or above #27, is a hidden shop which sells Medicine x2, Medicine x4, and Medicine x4 (yes, same item appears twice).