To buy equip in South America one possible option is
http://www.geocities.com/TimesSquare/Stadium/9281/eqengl.html (dead link)
They have foam GO boards (with the stones) and MDF (medium density fiber) GO boards.
In Argentina go sets are sold on the Asociación Argentina de Go
In the Koreatown store, Móron 3265, Cap. Fed., Buenos Aires, Argentina (Stones, boards)
There is also a manufacturer who sells quality boards
http://www.simpleko.com.ar/ (dead link)