Can’t Get The Transaction To Zip Along

(I go to a sewing supply store to get a separating zipper. The store is not self-service; you have to ask for your items at the counter. There are displays on the wall behind the counter with examples of all the items they sell.)

Me: “I’d like a separating zipper, please.”

Clerk: *brings ordinary zipper, the kind joined at the bottom* “Here you are.”

Me: “No, a separating zipper, please.”

Clerk: “This one separates, see?” *pulls tab up and down to show me that it opens and closes*

Me: *points at one of the zippers on the wall behind her* “I meant a zipper like that one.”

Clerk: *turns to her coworker and asks wonderingly* “Do we sell those?”