I don't know if anymore developments have happened since Sep 21, but then Reuters reported that the source of the planes that Argentina was looking for had not yet been decided:
Argentina is looking at buying up to $664 million-worth of multipurpose fighter jets to safeguard its airspace, the Defense Ministry said in a statement on Tuesday.
A source with knowledge of the negotiations told Reuters that planes from China, the United States, Russia, South Korea or Israel were being considered.
The process "is in the technical-economic and financial evaluation stage of five alternatives," the ministry said in an official statement.