For this deck, the contractor used 3/8″ diameter stainless steel pipes as a railing idea. The wood in this railing corner detail is clear western red cedar. The ends of the rods can be threaded and then secured in place with a nut. Or they can just float in holes drilled in the wood railing posts. You can find the cedar at a local lumber company. The company that sells the stainless steel rods is Alco Metal. You would need to determine what size and quantity and they could give you a quote.
This is such a clean look for a deck railing idea, and wouldn’t have the problems associated with cable railing. I especially like the use of the 2x4s for the bottom part of the railing. The thin stainless steel pipes really open up the view through the handrail.