I think I have a solution for you!
I surprise my kids with costumes to wear at
Disneyland every year we go during Halloween. I ordered my daughter's Zarina costume from the
Disney Store online back when the movie came out. Because my daughter is 9 (average size) it will probably be a little short, but I thought that was the largest size it came in (I saw a 9/10 on line at the Disney store afterwards, but I'd already purchased the 7/8 and it seemed like it would be too much of a pain to do the exchange, etc.) She wears bike shorts under skirts all the time anyway, so I figured she'd just do that, even if the skirt was short.
*Anyway* (sorry for all the backstory), I'm going to give it to her when we go on the trip in mid-October, but we'll be back 10 days before Halloween. I could just wash it and send it to you. (We're in Northern CA too). Honestly, I know DD9 would be happy to make some other child's Halloween dream happen, and if it really runs small, I bet this DLR trip will be the only time it would fit her.
PM me if you want to email or talk and I'll give you my contact info.
P.S. - I didn't buy wings, since I figured she would use her Tinkerbell wings--yeah, she's 9 but she *loves* everything Disney and doesn't feel at all too old for all the costumes--but it sounds like you already picked those up anyway.
P.P.S. - I have no idea why there is a red face at the top of this post. I could not make it go away!