Yes, I've made a dozen or so over the years. The principle seems to be long forgotten. Originally, the exact weight was carefully selected after empirical testing, with the specific goal of moving harmonic resonance out of normal cruising speeds to avoid 'buzzed hands". Since you are looking for cosmetics, any material will suffice, weight is not important. A round in 304 FM Stainless or 6061 aluminum is easily obtained and makes for quick work.
Most of the ones I've made were to incorporate a bar end mirror, or a throttle friction, and to avoid shifting when accidently bumped, I avoided the rubber plugs and machined expanding inner ends using a wedge pulled up by a thru bolt. When done right, you could stand on the mirror and not twist the bar end weight/mirror base.
Ciao,
Dick Casey