Bifold door missing hardware from pin

I have a bifold door that appears to be missing a piece from the top. The third photo shows one of the doors that has the full piece. The first 2 photos show the door that has the missing piece. As you can see, the pin is not secure in the door. I don't know what the missing piece looks like but it might be some sort of tube that goes around the pin. This hardware is original to our house, which was built in 1968.