Where can I find dowload for Admin Tools for M-Files 2018 (19.8.8114.8)?

The installer is included in the full package and in the desktop and server tools package, but not in the desktop only package. You will have to get your hands on one of those packages.

I'm afraid that the old installer is no longer available even through M-Files Customer support, as we do not keep all of the versions, and that version was released a long time ago. What is the need for this version? Why are you not updating the system to a more recent version? 

I've inherited management of this particular system. It runs well and does what they need. At least I can run the management tool directly on the server which is what I've resorted to doing. I'll look around and see if I can find the desktop installer on someone else's PC.