Sorry to hear you have a leak - on the bright side, you found it before closing for the winter. You can try the yellow pages for leak detection or divers - or call a liner pool company, they should be able to either do it themselves or refer you to a diver.

Those are the expensive ways. Poconos, the moderator, made his own patch applying rig he posts some pictures here

Good luck with it and make sure that that is the only leak.