Firstly, you need to be sure the voice coils have been fried. Test with a multimeter to get confirmation. The reason I mentioned so its not your amplifier that has stopped functioning for some reason :uhoh:
Once you have determined that it is your subwoofer ,then get online to see speaker repairers closest to you so you can obtain quotations for the work.
Good luck with it and hope you determine the culprit and then take steps to rectify it. If it is your amplifier, then go shopping for another one, mate!