If I were you, I'd NEVER go back to that bike shop again and I'd be sure they knew about my decision.

Ferrules of the type you need are a VERY common item. They should be able to provide replacements at no cost to you, especially since they were the ones who lost the originals.

That they did not offer them up right away, as in IMMEDIATELY, is a problem, too. It reflects a bad attitude (IMO). It should have gone like this, "I apologize if we lost your original parts. I'm sure we have some thing that's identical or will work. Come on back and we'll fix you up with some. Bring the levers with you, please."