PM John Barton and ask how the case comes apart. Just because a person is a saddle and harness maker doesn't mean they know how to disassemble a cue case. You have to pull the interior to be able to put a new rivet in most likely.
I had a Sterling repaired at a shoe and luggage repair shop. New thumb latches, had the lid reinforced and a zipper.
$75, but that was Canadian prices. It was very much worth it for me.
John told me that the little nails at the bottom had to be removed so the bottom could be taken out. Once out, the lining can be removed.
I don't know if the Instroke is similar in nature.
I know a guy that had the same repair as you. They just sewed another piece of leather to both ends. Might be able to do the same if there is enuff leather on the case end. Kind of a quickie hack way of doing it but it saves having to take the case apart. You couldn't see the repair anyway so it didn't really matter.