There are Army and Air Force Exchange (AAFES) stores located on bases all around the island.
Click on the following links for more information on store locations, hours, and contact information for each base.  

Camp Courtney
Camp Foster
Camp Gonzalves
Camp Hansen
Camp Kinser
Camp Lester
Camp McTureous
Camp Schwab
Camp Shields
Kadena Air Base
MCAS Futenma
Torii Station