I've seen actual Philadelphia cream cheese sold at several Disco and Jumbo supermarket locations around the city, sporadically. And at Tina&Co. in Barrio Chino. A very dear price, of course. Are you in CABA?
many higher end fiamberias carry philadelphic, and some discos and jumbos do as well. Bodega Amparo, which has a few locations, has it sometimes. almacen 1249, which has 4 locations, usually has it. Like everything else in BA, you could probably have it delivered. https://almacen1249.com.ar/
Seconding @Ronnie Hotdogs 's opinion. Finlandia (blue lid, full fat original) is extremely similar to Philadelphia and makes good cheesecakes. Casacrem is more of a fake sour cream to me (though even there it's not as close as Mendicrim).
there are actually some new, local cream cheeses that are really good.
this stuff is not cheap, but its really good. Juan Grande brand, in a plastic bag, you can squeeze it out.
I think its actually better than philadelphia for spreading, not sure about cooking.