I just love the "tell me all about what I'm picturing in my mind" questions.
As ChefDell said, there are many different kinds. But if you've already found something similar in the supermarket, you're already a step ahead of the rest of us: you know what they look like. If you've already been able to find something similar, the issue is not "where do they sell mints like X" but "where do they sell the particular brand and variety I like, or something very close."
Why not ask the owner of the restaurant you're talking about? Presumably he's buying them from a local supplier. Or ask for an empty package and Google it.
There are different mints in different restaurants. Are you refering to the ones that are covered in chocolate and are round little balls? Or the peppermints that are kind of puffy and dissolve when you suck on them? Then there are the kind wrapped in the Asian looking wrapper.......so many! I just re-read my post and at quick glance I should be sensored!!!