I think you can find the same kinds of outfits, but you'll just have to be more careful that they aren't too low cut, too shaped, etc. A denim skirt like
this from Old Navy would be cute, and the waist has some stretch to it. A denim skort
like this from Kohls would be good, too.
This one comes in colors; I like the turquoise or purple for an 8 year old.
I didn't see any good shirts on the Old Navy website, but maybe something like
this shirt from Kohls.