You can try down at Galleria Jardin.
But your best bet is to get someone to buy them online in the USA, and bring em down in person.
I have repaired a couple lately- my kids are hard on em- and parts are cheap and accessible in the US, but relatively rare and expensive in Argentina.
I paid 39 bucks USD for a new screen, for example, I cannot imagine they are anywhere near that cheap in BsAs.
And the damn things break pretty easily.
Luckily, a screen replacement is not hard.
I have done two of em for my 19 year old in the last year, since he would otherwise have to pay full retail for a new phone- $550 US for a 4.