So, is the compression ring actually present and the screws are somehow frozen?
The compression ring is nothing more than a thin strip of brass fed into a slot. Many people on here have made their own replacement ring, it isn't overly difficult. The material is readily available at craft or hobby shops.
So, the brass ring is in place. The problem is that one screw is frozen, (broken off), and the other has very little travel, and I fear could be non functional at any moment. If not the compression ring, then I'm not sure what the part is called that holds the screws that hold the 2" eyepiece in place? That's what I need to replace.