Bucket seat adjusters

My 70 Cuda bucket seats has Adjustable bolts on the bottom inside corners of the seatbacks and they are just bare metal. They have worn through the upholstery material, leaving holes in the material. Are the adjusters supposed to have some kind of rubber cover? If so, where can I find some, or even two knew bolts with the rubber on them? I'm putting new seat covers in and would like to correct this before doing so.
Author: heminut