Ok color me overly concerned about the ability to insulate the 3 materials from each other. Just keep going forward and juice the area regularly with oil or whatever in the future.
Maybe it's English that i don't speak. They are the ones that call a wrench, a spanner. Presumably a ring spanner is a box end wrench in american speak. inches, pounds, wrench; what's wrong with the rest of the world? ha ha

My hair brained solution would be to wet out a bundle of carbon tow about half a meter long on your plastic covered work table (you can un-weave cloth to get the strands if you don't have the tow). Squeegee it out with your hand by pulling through a fist. Make sure the bundle fits through your rivet holes. Once squeegeed out it holds shape pretty well.
Guide one end through the hole and clip off a section with scissors. Flair or fold over the top end so it doesn't fall through the hole and tape off. Figure out some way to fold or flair the bottom end, and a way to hold it like that until cured; like a plastic covered stick, tape, a bladder, etc.
I have never tried this exact procedure, but i like to use carbon and resin to replace as much of the metal components as possible.
If you had a carbon beam, bracket, and traveler track, it could all be glued together in theory.