If you want something specially made, you can always commission it from someone who does cosplay work. You can find people in cosplay groups (such as on Facebook or Reddit) who are looking to take commissions. You do still need to purchase the cosplay in advance since they are usually made-to-order. You can’t control the fabric/material choices that are made. If you don’t know how to sew or add detailed embellishments to a costume and don’t really care to learn, then you may as well buy the costume.