I got the radius rods made by Wisbech Engineering, They are polished stainless steel and supplied with Polyurethane bushes (Axle end) and Spherical rod ends (Chassis End).
Here you can see one of the Radius rods, they are mirror polished stainless. I had them made with 44" centres and by using a little bit of simple trigonometry worked out that the end should be mounted at 8 degrees. You can see the rod end and the bush end at the angle.
I made the brackets to mount the rod ends on the chassis from a piece of standard steel box section cut at an angle. I then trimmed the bottom edge off and gave them a nice rounded shape.
It was then just a matter of welding the brackets onto the underside of the chassis.