Final answer:
The sales associate should direct the customer to the store's custom drapery department to assist with creating curtains in the non-standard size.
Step-by-step explanation:
The sales associate's best response would be to inform the customer about the custom drapery department in the store. The sales associate could guide the customer to that department where they can assist with creating the curtains in the non-standard size. They may also provide options for customizing the curtains, such as adding extra fabric to allow for hemming or altering the length.
Learn more about Providing assistance in selecting curtains