yeah i was looking for one for my ‘79 2 seater as well but they were pretty expensive for original ones. I ended up finding this parking brake cable kit from Wilwood that I was able to use. I currently have it installed in my Z and it works really good and it wasn’t that difficult to install.

https://www.amazon.com/Wilwood-330-9371-Parking-Brake-Cable/dp/B002G39K0A