I had some 4 pin connectors that I bought a while back. They fit OEM in some places, but not others. They did not fit the OEM rear speaker 4 pin connector. But, I cut one of them up a bit and forced it into place. Then taped it all up.
In other words, I do not know exactly what connector you need or where to get it. I know that mine did not work correctly. Hopefully someone else will chime in.