So the conclusion to my saga is this: I went to unicenter because they had a whole bunch of shoe stores as well as a flagship NB store down the street. It seemed like the easiest way to visit a whole bunch of stores quickly which it was. While it’s true that stores stock size 12 in theory, the reality is most had almost nothing to choose from. Compounding my problem is that I wear size 12 extra wide (4e), which apparently doesn’t exist in Argentina. NB had nothing, Dexter had one pair, same with Nike, and so on. I finally found a pair of $8300 size 13 Reebok’s at their store that I wouldn’t have bought at home but they’ll work.
Thanks to all for your help and suggestions.