What part is this? (Cooling system, 1994 Voyager 3.3L V6))
 

I noticed coolant leaking from the bottom of the engine (driver-side).

Here is a photo of the engine where the rusted component broke off:
https://cimg4.ibsrv.net/gimg/www.chr...5a68b372ee.jpg

This is the component I'm trying to identify and purchase:
https://cimg5.ibsrv.net/gimg/www.chr...72025edcb3.jpg
Rusted component; the back side is flat and fits in the orifice in the top photo

This is where I am looking, but cannot find anything in 'cooling system':

1994 PLYMOUTH VOYAGER 3.3L V6 Parts | RockAuto

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Thanks in advance for your consideration.