Why not go a few 7 stops down to Jackson Heights and Woodside? There are Uruguayan and Argentinian stores starting in the 60s (only a few) and then another concentration in the 90s. There are also a bunch at the intersection of Corona and Junction.
Alfajores Havannas? They sell them at El Gauchito (Argentine butcher/ restaurant) on Corona. They are EXPENSIVE, like $20 per box. The C-Town supermarket across the street also has other brands of alfajores, but I don't think they have Havannas.