How do recruitment consultants reach companies?

Hello,

The following question: HR consultants have to create a file of candidates who are looking for a job, so it's clear how it all works.

But how do you find companies that are willing to pay the high commission, as long as you haven't yet built a business network? Can you only find them through advertising and/or by chance, or is there software or something else that can help you find these companies?

Thank you