Sim card stuck because of missing piece

I have an iPhone 7 plus that I was working on for fun and I got the issues all fixed… broken cameras, no service, and damaged rear housing. However, I have an issue with the the sim card now.

The issue is that there is a small piece that goes in between the logic board and the iPhone rear casing. On my phone, that piece is missing. It is a black metal/plastic piece. This piece is what the sim ejector tool pushes on to unlock the sim locking mechanism on the logic board as the tool cannot reach that far.

I was wondering if anyone knows what that piece is and where I can buy one.