That is the $64,000 question. The original chair uses some custom brass hardware mounted to the back of the backrest after weaving. The strap bends around the side and has a pin that fits into a socket in the side of the arm. I have been scouring the internet for something like this, but haven't been able to find a close match. I have some Amazon pivot hinges on order that will probably work, but will be a bit clunky. I've been toying with fabricating them myself from brass stock, but I've not done metal work since shop class in high school. I may go for it to get the custom look.
I do have a question… I see how you used a bevel gauge to capture the angle at the end of the rail. Why do you then switch to that transparent compass to continue the process? Could you have used the bevel gauge instead?
Thanks, Ron. I just used the plastic gauge so I could read the numeric angle, which I then set on the miter saw. I didn't need the miter angle to be super precise, and setting the saw angle directly from the bevel gauge 8 times (twice for each rail) was more than I wanted to do for an angle that just needed to be relatively close.