Argentina is in dire straights due to them being considered an enemy of Britain and having what is thought to be an unstable economy. Here is a good read. The Russians haven't said no to the Mig-29 but the range is not good enough even with external tanks. Argentina can't afford the SU-30s new and there aren't any on the used market. I won't reprint any of the cite I am giving but it's a good read in a chonological method.
Two to Tango? Argentina Looking Everywhere for New Warplanes
The West won't sell them anything other than training AC right now. And even if they did, financing from the west just wouldn't happen. It would be cash and carry. Russia might cut a deal with them and help them finance it though for used Mig-29s just to poke Britain in the eye over sanctions. South Korea and the US will sell them the 12 pilot trainers though and it looks like Argentina can afford to pay for those.
Argentina has pretty well painted itself into a corner. Their economy is a mess. Anything using British parts or US parts (including the J-79) they can't pay for. Even when they already own these sooner or later they will have to take the bird off the line due to not being able to purchase spare parts.