Morinaga Milk Kasugarenmilk Tube-Shaped Pouch Book" by Takarajimasya, designed to look just like the real thing and with a large capacity!
Takarajimasya sells "Morinaga Milk Kasugarenmilk Tube-Shaped Pouch Book". It looks just like the real thing except for its size, and has a large capacity to hold about 12 pens.