Rear window track parts

[Dustyrides]

When I got my 68 GTX these rear window track roller parts were laying inside under the rear window assembly. I can see where they go but it seems like they are missing a bushing or guide of some sort that keeps the spherical ball in the guide rail. is this something that can be purchased new or a simple part that can be made? If anyone can help with the proper name for it or a picture that would help too.
Thanks

 

[snakeoil24]

this is for 1/4 window and you cant repair it. The other side must have cracked off. They are molded onto the ball on both ends. RT specialties caries them