Eric, maybe these photos will help.
The first was taken at least 10 years ago and shows the door-top capping, in place with a rusted end button.
The next photo shows a capping that has been stripped except for the basic capping piece and an end button. The end button is complete with barbed clip.
The next photo shows a capping that has been glass bead blasted and powder coated and ready to be covered with new leather.
Finally, I have added a sketch from a Roadster Factory Catalog, showing the component parts that they can supply. You can find it here:
TRF mini TR2-TR3
The re-covering process is very simple. For each door-top capping you need, new leather for covering, 2-new chrome plated end buttons, a length of foam rubber core, and adhesive. Cut the foam rubber core to fit between the ends, and cement in place. After this has dried, spay adhesice, cover with leather, be sure to tuck in neatly at the ends and glue and push the end buttons in place. I used adhesive tape to hold everything together while it dried.
Good luck!