Not a hamster, but a cat. They are called Nemuneko. You can find them on Amazon with its name or in smaller shops for japanese stuff on google. Just checked.
https://www.amazon.com/FuRyu-Nemuneko-Fluffy-Plush-Large/dp/B01M0HMGQH/ref=sr_1_8?s=toys-and-games&ie=UTF8&qid=1499176564&sr=1-8&keywords=Nemuneko this is?