Replacement Radio Antenna

Somehow or another I have lost part of my radio antenna. The antenna s very common on Keystone campers yet I am unable to find a replacement. I have no issues where it goes through the roof or anything else I need just the antenna part. It is the one with a spring about 3-4 inches long with the rod about 18 inches long.

Any ideas? All I really need is the rod.

Thanks
Bryan