I'd recommend Etsy! There are sooo many cute, ruffly, pink and purply, sheer chiffony panties! I've favorited SO many. I've also found some shorter, novelty printed skirts there when searching under "lolita" - a lot of lolita stuff appeals to my little side.
I found some fun lingerie on Forever 21, too - they have panties with animal faces on the butt and even EARS on them! And fuzzy sweatshirts with ears on the hood.
I think you can find little clothes anywhere you look. Hair ribbons at a fabric store, headbands at Target, a cute short skirt at F21, jewelry at Claire's or the Hello Kitty store... you should take a trip to the mall and just amble around and see what strikes your "little" fancy