Teen plus size/curvy fashion?

Hello!
As a lover of fashion (I'd like to be a fashion designer one day, and maybe start a line in Japan if possible) I wonder, is there stylish clothing for slightly bigger teenage girls, around what would be the equivalent to a Junior's 11 or 12? I'm pretty short (5 foot) and kind of chubby. I plan to visit Japan one day, maybe for my birthday next year, and maybe live there if I could find success in fashion.
Rambling aside, I am really curious about this. I love cute, pretty clothes and I like to look girly and pretty every day, but I've heard it is less common to see girls that are not petite. Japanese girls are usually so adorable and small, and it worries me that while shopping, I won't be able to find anything...
Please, your help would be very much appreciated. Thank you.

Try su*pu*re - http://www.rakuten.ne.jp/gold/suzutan/

Or Monster drops (maybe a little too old for you but very cute) -- http://www.monsterdrops.com/

Shimamura may also have a few things for you. I'm not sure what 11/12 junior size means, those clothes may be too big for you.