I blogged about my other Japanese erasers a while ago. Those were sold under the name Crazerasers, by the company Fashion Angels, while these are sold by a Japanese company called Iwako. These are sold for about a dollar per eraser. In Japan they actually have eraser stores that sell these erasers specifically; I've never seen one of these where I live though. However, you can buy these things online. They come in sets on Amazon. Places that sell them individually include erasercrazy.com and zoolicompany.com.