1999 Ford Escort What is this part?

I have a 1999 Ford Escort with a leak. It's an automatic, and that's about all I know about cars. The leak is coming from a part in the transmission. I see three of these parts, but only one is leaking. There is a lock ring holding it down a plastic thingy with an o-ring around it. Under this part is a spring and dirty looking liquid (I'm guessing is transmission fluid). I broke the part trying to put it back in, so I used J-B Weld to keep it together. I purchased an o-ring from the local auto parts store and stretched it to fit. I'd like to replace the part, but I have no idea what it's called or where to look to replace it. I added some pictures of the part.

Also, I added a picture I found on this site (relating to another topic) and circled where the part is located in blue. The red circle is something else, whatever the picture was originally talking about.