You may want to email Grado labs ,but they usually don't sell drivers ,you have to send them in for repair.Since you are in singapore that may be a
problem maybe Jaben can help you out. Or look for someone that has a used driver.
How did you solder the wires on if you didn't melt the solder? The voice coil wire connects to the pad under the white clob you see in the pics you posted between the two cable wires on the driver. .