Took it to Coach today and they sent it in for repair. Think happy thoughts
I hate to say this - beautiful bag, btw, but I had a Legacy Ali sent in about 4 years ago, similar issue, although what happened with mine is that the part of the turnlock that spins broke off, not the entire thing. I sent it in, and got it back with a letter and a coupon (which was very nice of them, as it was an old bag at that time). I don't think they have the hardware. What I did (again, the base of my turnlock was still there), was very carefully open up the lining on the pocket with a seam ripper and then thread a toggle button (black and wood because there was no way I was matching the finish on the hardware) through on a leather cord, that was selected to fit the whole on the flap. It worked, and I just put in Velcro in the lining where I had opened it up - I figured that eventually that button might fail as well, if the leather cord was worn through. It worked fine, and was the best that could be done. You could probably do something similar, but through the holes left by the turnlock? Or find one of the smaller bags that has the same size turnlock and harvest it?
Bummer!