I hope you will find what you want in the end. I think the stock condition is the most desirable thing to look for in a used BRZ, then mileage, maintenance, etc. I worry about the used manual cars since I know so many not-so-talented drivers abusing their transmission/engine/clutch. I have my bias not to buy a used manual car. Even an idiot can drive automatic without as much abuse. But BRZ automatic is not the same automatic you would find in Yaris. If you have the opportunity, go drive one automatic BRZ and you will see what I mean. You can drive the automatic BRZ in manual mode and shift in automatic mode. So if you find a desirable automatic, I recommend give it a look instead of indefinitely waiting. Not sure if you have seen the following video, I have a very similar configuration and I love it.
Good luck!