My son managed to break the derailleur of his Mongoose mountain bike without any accident. I was surprised to notice that the piece that connected the derailleur to the hanger was actually made out of plastic (obviously didn't pay attention when I assembled it).

I located the direct replacement based on the model number but I am a bit hesitant to get yet another plastic one. I understand it's designed to break without harming the frame but biking around the neighborhood didn't really stress it so wondering if another 7-speed derailleur will work. How do I identify a compatible one? I see many options within the same price range without the plastic part.

Can't post any links or photos yet. Here is the derailleur - amazon com/INKESKY-Shimano-Derailleur-RD-TZ31-Mountain/dp/B07GV14SLS/

Thanks for any suggestions.