jbl wont sell you one?
you might have to find somebody with the same product and ask that person to get some values from the power supply while it is functional.
you probably need to know the output voltage.. perhaps the frequency that the voltage is being output at.
and lastly, what the impedance of the power supply is.
you are gonna have to find somebody that has one so you know what you are shopping for.. otherwise ask jbl service center.