These aluminium throttle tubes can be adapted to use with a regular bar end.

They come standard with a rubber bung in the end, so are "legal" with just a grip over it, but as most of us like to protect the end of the grip a set of bar ends is also possible.

Use the ZETA bar ends we have available, and replace the internal M5 button head screw that holds the bearing slug, with a longer M5 screw that also will then hold on the bar end.

I have attached some images in the description as reference. It's an easy job (two allen keys required only - one for undoing the screw, and one to holld the slug from rotating)