As one can see from the photos the top part of the plastic top pin has broken. The brackets attach to the plastic pin hold and hold the pivot into a heavy extruded aluminum top channel. A an replacement would be great or recommended alternative. The dimensions of the brackets are 1 1/4" by 5/8"The plastic piece is 1 1/2" long. the brackets are held to the plastic pivot by the single screw -- one bracket is threaded and the other fits on the opposite side and is held on the plastic bushing by the screw head.
Thanks, james