Trying to find a part for 1993 Hatchback lock acuator

So, my car got stolen about a month ago. I got it back from the shop about 2 weeks ago, but one part wasn't finished. He couldn't find one tiny little plastic piece that would complete the assembly of the lock on the hatch. There is a metal extension off the lock tumbler, this metal extension fits into the plastic piece I am missing which then turns to pop the lock.

I need this piece and will do (almost) anything for it. Right now anyone can pop my hatch with nothing but a screwdriver. If anyone can point me to a site that sells it, or even tell me what the piece is actually called, or if someone has one they would be willing to sell me, PLEASE post or PM me!

Here is my (currently piece-less) lock assembly:


Here I've highlighted where it goes:


This is the lock assembly off a 1991 hatchback, with the plastic piece in place:




Needless to say, the one off the 1991 will not work. Apparently, the only part that will fit is specifically off a 1993 Mustang.

Thanks in advance.

I did check there, and couldn't seem to find what I was looking for. I wouldn't know what it would be called if they sold it seperately, but I also didn't see that specific piece included with either the entire latch assembly or the lock/key set. Thanks though.