Here is a link to the only seed source I've been really happy with. I don't know regulations for shipping to Argentina though.

E-Bay has tons of seed for sale. Once again there is a possible shipping/customs issue.

Personally I have a young generic red maple in my front yard. It seeds earlier in the year up here...May? if I recall. Whatever samaras it dropped are well in the ground doing their thing by now.

Here is a link that might be useful: FW Schumacher Seeds