Make your own giant, the entire wall, whiteboard for practically nothing. Go to your local lumber, home building supply store and purchase "laminated particle board, shower wall panels". Last time I did this, they were about US $23 for a 6'x9' panel. Two of these completely cover an ordinary single bed sized room from wall to wall. I just drill the thing right into the wall, and grab white-board markers. I showed the building maintenance manager this trick at an animation studio I worked, and in a week the entire studio's walls, every wall, became a whiteboard. Scribbling ideas, any idea, on one's wall is liberating.