To buy equip in South America one possible option is
http://www.geocities.com/TimesSquare/Stadium/9281/eqengl.html
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
http://go.org.ar/ventas/index.html
There is also a manufacturer who sells quality boards