You might be able to order this part through the sony parts/service site, I have bought the other side attempting to make my own power plate. I have taken apart both sides of the dock, it's not very hard.
It is also normal for the top dock not to have the power connection, only the back dock.
You can live without this connection however. The 4 pin of the IF box is what connects to this port. The IF box will still work fine for Dual Link the power isn't needed to power the IF box, it only sends it into the camera. Buy the Abelcine F65/35 plate with the main power lemo connector. I believe it is safer to use the main designed for power and also you have the benefit of the aux power outputs on the side of the camera working.
That's what I was hoping someone would say, thank you! I'm currently powering through a Bauer gold mount plate on the back. While I was hoping to have the option of AC powering the head through the IF, it's a minor thing. Cheers, yachacha.