Does your 2403 controller have the same wires and connectors as shown in the wiring page linked to below?
A 2403 controller with the same wiring and connectors is not going to be available so the best way to get it running again is to custom install a new controller and use its wiring directions to wire all of the parts to it.
On an old scooter like that the batteries are sure to need replacement also so at minimum a new set of batteries and controller would be needed.
The label on the motor will help determine which controller is needed. For example, if the motor label reads 24V 250W then a 24 Volt 250 Watt controller such as our SPD-24250 or SPD-24250A would be suitable for it.
Judging from the controller model it is most likely between 10-15 years old.
The motor in your photo is a 24 Volt 200 Watt motor so a 24 Volt 250 Watt controller such as our SPD-24250 or SPD-24250A would be suitable for it.