Towing/trailer question?

Hello. I have a trailer that has a 5 pin connector. (5th being the electronic brake assist. However, it does have an inersia based breaking system as well. When it feels itself getting closer to the truck, it applies the breaks.

On the back of my truck, I have a 7 pin connector, and a 4 pin connector.

The 5 pin connector on the trailer is not long enough to reach the truck. I need some sort of extension cable/ converter.

Where do I find a 5 pin to a 7 pin cord?

I have a brake controller, but I have not installed it yet. So I do want to have it in the 7 pin connector, so it can utilize the electronic brakes.