Where can I get Japanese Yen?

My sister is really into Japanese culture, and while she is too young to go to Japan by herself (and it’s too expensive for anyone we know to take her), she is still interested in everything Japanese.

Well her birthday is coming up, and I would love to get her Japanese Yen as a present. Other than Canadian coins, she has never seen any type of currency from other countries. So I know she would LOVE Yen as a gift.

Where can I go to get some? I would really like to get all the denominations under USD. Are there any websites?

Thanks!
I’m looking for all types of Japanese currency, not just their coins!