I have exactly the same issue as you did, I am looking to replace at least one of the female parts of this set as it shattered into pieces. Did you have any luck finding or making a replacement?
I was able to take a big washer and drill the holes for screws then JB weld it to the threaded two inch sleeve. No way I could find the replacement piece because the manufacturer went out of business in China. Hope this helps
Try Rockler's website for woodworkers. i believe they have something close. You might try Carr McMaster as well because they seem to carry most everything fasteners.
I know this is an old thread, but I had the same problem. Brittle "pot metal" insert that shattered into a gazillion pieces. Looked for months for a replacement. Finally found one on Amazon, shipped from china, that is so perfect that I don't even have to replace the threaded portion. Details below. Cheers