Sydney's Closet only has one store location is St. Louis, but you can purchase bridesmaid dresses up to a size 44 from their online store and ask a local seamstress to make any needed alterations.
You may want to commission a seamstress to design and/or sew lady bug bedding sets, cloth wall hangings, etc. Finally, don't forget to check out Ebay as you search for lady bug accessories and nursery bedding.
Again, you do best to work with a professional designer or seamstress and have the corset fitted a few times during the construction, but if you can't do this, there are some good online designers.
That CEO who just joined the church may also be an accomplished seamstress or tailor who will sew beautiful costumes, and the quiet artist who sits in the back of the sanctuary every week may be happy to design and paint props.
If there is not a local seamstress who has experience with such projects where you live, there are people online (such as Dance Sport Ballgowns, above) who will take your measurements and make a custom gown to your liking.