Gah, after having the things off and on bikes probably a dozen times, one of my old Suntour barend shifters just stripped out the Allen drive in the tapered mounting screw (the one that expands the three wedge things) when I removed the shifters to swap brake levers. May be able to reuse it by driving a next-size-larger SAE Allen wrench into the end (it was by wiggling one in that I was able to get it out), but it'd be goofy having different drive sizes right and left. I know I've seen the bolt things for sale on eBay and elsewhere, but can't remember what they're called, and don't know if the Shimano ones are the same or not.

If all else fails here's a way you can continue to use them. Grease the ramps on the wedges front and back along with the screw thread. Then coat the outside of the wedges with a traction compound, either lapping compound or carbon assembly paste. Then adjust the wedges for a snug push fit. Tap it in, then rotate the body to tighten. Obviously it'll take some trial and error to get it to end up vertical when it's tight.