Where can I purchase the manga series Heart by Rie Takada?

I don't want to read it online (already have on mangafox) I now want to purchase the entire 10 volume series, but can't seem to find it anywhere. Can you please help me by pointing me in the direction of where I can purchase this manga series? I can't find it on Amazon or Barnes & Noble. I'm at my wit's end. Can you please help me?