Já už si to moc nepamatuju, ale podle zdroje dole :
On Roche's path, Seltkirk's armor can be looted from the body of Vinson Traut in the basement of the old tower in the camp followers' encampment during the quests "Conspiracy Theory" and "Courage Symbolized".
When choosing Iorveth's path, it will be obtained from Philippa Eilhart.