Such a dress can be purchased, of course, but without special ordering, most stop at size 6x. My 6 year old girl child is in the 90+percentile for both height and weight in her age category, so she has long since outgrown such a thing. Besides, store bought Disney dresses are always made from cheap, crappy satin that runs/deteriorates faster than the child learns to fasten the velcro. So I went to the fabric store and bought 2 yards of lavender knit. "Use a pattern, Jenny!" my mother implored. But why would I listen to her?
places (that one there has photos of how the store-bought dresses wear out, along with a thorough how-to) and one of them (I can't find it, but this shows the same concept) showed the ribbons as just stitched down. I went with that. No grommets (which are fun, of course), no fuss. Well, some fuss. I made the top based on a Simplicity top I've made her a half dozen times. Then I sewed on the skirt, made from a rectangle sewn into a loop, pinning a lot.