Is there a way to search the MacMost exclusive posts at Patreon?

Go to patreon.com/macmost and look for the Search field.

Yes. Go to patreon.com/macmost and scroll down to the Recent Posts section. Look for the Search Posts box and type in your search phrase. Or, if you use the search box at the top of the main MacMost.com site, you will get results both from the free content at MacMost.com and the exclusive posts at Patreon.