Friends, I found a workaround, albeit clunky.
I created a copy of the member page that I wanted to be searchable (yes, you have to copy each blog post) to a public, but unlisted page. I made the slug for that page a bunch of nonsense so no one will type that in and made it unsearchable for search engines.
Then, in the members area — I created a search block to only search content on that unlisted page.
It's not the best, but it works. I put hours into a site for a client and then realized that search wasn't an option (something they were set on). It was either this or starting from scratch on a different platform.