Use robot parts by a company called Actobotics. They are easy to find at robot suppliers. Servo City also has them. I considering them for the stabs on my F-105 project.

Get one of these hubs and bolt it to the arm below. They are like erector set parts and all fit together. The bore sizes are common sizes. 3/8, 1/2" etc.



Some links:
https://www.sparkfun.com/products/12177

https://www.sparkfun.com/products/12519