Given that the UK can block 'as is' supplies of FA-50, Gripen and Tejas, I guess that the best option for Argentina is probably Spanish Mirage F1 (to be operated for a limited time) or MiG-35. Short term use of Mirage F-1 would give Argentina the option of buying a modern no 'component supplier restricted' Tejas Mk2 in the 2030's. By that time Tejas Mk2 should have an engine freeing India from UK/US political constraints on who can buy Tejas Mk2. Russia - still needed for the ejection seat - could still block supply. Unless India decided to get into the ejection seat game in the next few years and came up with an adequate product.
The Argentine Air Force could buy LCA Tejas from India refurbished without British-made components - The Aviation Geek ClubThe Argentine Air Force could buy LCA Tejas from India refurbished without British-made componentstheaviationgeekclub.com