For my truck I purchased a ratcheting cargo bar at the local auto parts store. I attached adjustable rod holders to the bar ratcheting all to the truck. Bought them on Amazon. You can use PVC for less money. My homemade rig works well and was significantly less costly than those advertised.
I tried to attach a pic, but got an error message: content too large. If anyone is interested shoot me a PM and I will send a pic.