I don't think you've chosen the best place for suit shopping (or any kind of clothing shopping for that matter). I'd also suggest that you try the international designer labels, but I heard on here the other week that a lot of them are nearly empty because of import delays and restrictions.
I can't imagine you're going to find much at all going into spring/summer but you may find something at a shop like Chocolate (there's several branches...alto Palermo has one) which usually stocks pretty muted tones (though I have no idea what they'd have in the range of suits). Portsaid, Markova and Kill usually have formal womens clothing too. If you can get away with a skirt and shirt, you might have a bit more luck in the shoppings.
I've never found anything commercial that I would describe as a "good quality" woman's business suit here. They're also not common so the vast majority of the suits I've seen here tend to be more cutesy and social. (ie, no ruffles on a business suit please)
Zara quality is a joke - they're known everywhere but here as a place to buy disposable clothes you wear for a season and they fall apart. Cheap prices = cheap quality (although here, not cheap prices but still bad quality which baffles me).
Anyway, rant aside, if you can find a good seamstress, it might be worth looking into getting something custom made. Otherwise, stock up when you travel if possible.