Where is the last eggman detector in sonic chronicles

The 5 Eggman Detecters are:
•Green Hill Zone in the cave near Cream the Rabbit.
(You have to fight 2 Scorpions)
•Mystic Ruins.
(Follow Shadow)
•Mystic Ruins.
(The left of the plane)
•Central City.
(Talk to the sad robot near a Eggman hide-out)
•Central City.
(Talk to the shopkeeper near the store and he'll tell you about a salesman he met in Green Hill Zone.
Go to the salesman to get back the shopkeepers stapler back.
Give the stapler back to the man and he'll give you the Eggman detector)