Client needs to know everywhere they are mentioned on the internet

So this is a novel and specific task I haven't come across before. Hoping this community can help me.

A client (let's say X) wants to know all the places online that they are mentioned along with another company (Y).

This includes all the webpages, social media posts, news articles, and every other online URL where X and Y are mentioned together.

X and Y have had a relationship over many years and across many countries, so it's going to be quite a long list. The list I submit needs to be comprehensive, preferably exhaustive.

Can someone tell me how to go about doing this? What tools will I require? If you've done this before, what are some pro tips?

TIA