I used an epoxy putty back in ~2000 on a set of throttle bodies on a TL1000R. It never flaked and was able to smooth it flush, on the interior.Found a hair line crack on the last runner on the throttle body. May have it welded, may source a used one. Depending on what I can find.
I can't remember the exact stuff, but I got it at either Lowes or HD, it was in a tube, and required minimal kneading, no messy liquids, I think it had dark grey and white and you kneaded it until it was a uniform light grey color, then apply it, cures in 24 hours.
Find it with the other loctite and JB weld stuff.
Btw the cracks on my stuff were a lot worse than that little imperfection.