Post-Office-Style-Eraser

Ever since he started school, he's been diligently loosing erasers and pencils everyday. So one day while I was doing some sewing, I just used some string and tied the eraser to his pencil box. And he stopped loosing the eraser. However for his pencils, I have used big striking colored sticker so he can see From far who is using his pencil so he can take it back. One eraser can use for a long time if they don't loose it. Things are not getting cheaper these days.