post privacy when making post inside page

Hey guys, so you have this option to choose privacy when a person making a post on his page.


But what about pages? Yeah, I can choose privacy for the whole page. But what if I need one post on a page is open for all and another open only for registered users?


I'm pretty sure that this should be very easy as cooping few lines of code from "posting as a person" template to "posting as a page" template.
Could you advise me where are all this files Thank you!