I sold a Pull For Floor placard with screws to Don Byars (Full Throttle Panteras) a while back. Maybe he is not using it and maybe he has a cable or knows of one.
The black round base is as pictured. It is the mount that goes into the square hole. I think you are on track if you need to make one.
Let me know if you need more pictures although it maybe some time before I can take them.