The one I used is called Alteco, super glue.
Use the kendama a bit first to blunt the tip a bit so it won’t stab the tama, sand it down smooth, then apply glue as thin as possible. Take a piece of paper or tissue then VERY quickly rub the tip against the paper in spinning motion back and forth, it will make a nice shiny layer of glue, repeat once or twice more if necessary. If you did it too slowly the paper might stick on the tip (easily fixable with sandpaper though).