What is this piece? Where can I find it

It is refered to as the kick down linkage ( really it is the throttle pressure controle linkage)

Without it the transmission runs at very low pressures and can burn up the clutches.

Mymopar.com has parts books and Factory Service Manuals free download.

You can find the part number there.

If push comes to shove you can make one from flat stock and with the help of a torch form the curve in the end.