As
@gopbroek indicated, pretty much every shop has private guide available subject to Covid space restrictions. Most also have divemasters whose strength is finding small stuff. It is also easier to find small stuff if you don’t have a big group to worry about, so a private guide is a good idea if you have the means.
That said, Fernando at Pelagic Ventures is really good for finding macro stuff. I have friends with 10,000+ professional dives in Cozumel who are very envious of his ability to find small stuff (kind of a running joke at this point about what did Fernando see today ). Certainly not the only good macro guide in Cozumel, but definitely worthy of consideration.