I happen to have my Z987 open now to replace the digitizer and LCD. The USB/charge port is soldered directly onto the motherboard. If your problem is due to damage to it, then I'm afraid you are out of luck unless you are very handy with a soldering iron.
Here are some trouble shooting tips:
* Obvious damage to the charge port
** Replace the motherboard
** Take your chances with a soldering iron (if you can find the right part)
** Get professional help
** Get a new phone
* If there is no obvious damage to the charge port, then you may have an easier problem to solve.
** The phone powers on when it is plugged in to a USB port
*** The problem could be a bad battery
*** The battery cable may have disconnected from the motherboard.
** Otherwise, there may be non-obvious damage to the charge port, see recommendations for obvious damage to charge port.
I hope this helps.