It should be included in your visiting list if you're planning to visit Japan. It is DonQuijote!
DonQuijote, Akihabara store offers very "Akihabara like" goodies such as Japanese idol products(lightning pen/fan etc.). →close to cashier on 2nd floor
Also, there are so many interesting products which useful for events like parties and cosplay.→5th floor
I saw many items that Japanese idol followers can use for autograph session, name plate etc. You may find something new items.
Especially DonQuijote, Akihabara is in the building with maid cafe and arcade. Visitors can enjoy an Akihabara like experience and shopping within this building!