You build them yourself. Sometimes they find you like others have said. But most of the time there is usually in your network somebody already trying to build their social clout that you can lend them your platform to help achieve both your goals.
Influencers out of your network don’t really give you that big of a permanent boost. You want people that could be in your network. And network theory you want super connectors otherwise known as influencers. Just remember that and don’t get tied down to the idea of influencers being young hip kids.
They can be a good business owner, a mom, or a meme account.
Any young kid with a large following without a vision or thought behind why they have a large following isn’t really worth it in my opinion.