Those ends look very similar to the ones I had on the cargo cover in my '90 XJ. You may be able to find some old XJ cargo covers for sale, or see if they offer the end caps as a repair item.
It may be possible to repair what you have using some threaded barrels JB-welded on the central post and then JB-weld washers with the bolt that fits the barrels into the end caps and thread them back on.
1970 1414X Wagoneer "The Pig"
-Dauntless 350 V8
-D27 front/D44 rear
2006 XK (65th Ann Edition)-DD