I had a much more successful day today, finding the brake cable I need. I ended up going to Clarence Street Cyclery in Sydney where they had both the brake cable and the cable housing! I was really impressed with their service and amused at when they asked me what kind of bike I needed the cable for, and when I said it’s not for a bike, they were very confused.
Now that I have all the cables, I am almost ready to start construction. All that I need to do now is order the set screws for each of the vertebrae and 3D print the first test vertebrae so I can test my concepts.