They do basic alterations on their costumes. The rental department has a ton of variety. I would go there with a picture of what you want to create. If they are not totally "Halloween Slammed" they will take the time to help you construct it if they have the parts. I have had great luck with buying certain pieces from the retail side, and renting other elements to bring it together. This place is really special.
No custom work done here. You will have to call and ask about the cosplay costume.
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