I am pretty certain that high quality memory foam in sheets doesn't exist in Buenos Aires. A few months ago I searched far and wide in all the big stores (easy, falabella, walmart) and small (think bed supply boutiques and mattress stores)
BUT i did find sheets of foam that served as a mattress pad for only 13 pesos. It was a small store on Scalabrini Ortiz a few blocks past (southwest) of Corrientes intersection. I forget the exact cross street. If walking from Corrientes, it is on the right side of Ortiz! The store sells fabric and foam pads. It is not Tempur Pedic but could work for you.
