So, I am providing the download link to the Install Assistant package from Apple servers. But among the developers, there are users who are willing to provide the link to the others users. You can also get it from the Apple servers as long as you have a developer account. The good thing about the Install Assistant is that it is provided by Apple for the developers. And when you install the Install assistant.pkg it will combine them and extract them on the Applications directory.
Install Assistant is not a very big deal since its only purpose is to contain the macOS’s data in a cage inside itself.