I just did it a week ago on my LX150. Bought a set of Suzuki Hayabusa bar end weights (how's that for irony!?) off eBay just because I liked the looks and they didn't cost much.
They are tapered chrome-plated billet aluminum and only weigh a few ounces apiece, but I wasn't doing it for the weight/stability (the LX has no wobble problems). I wanted them for the looks, and to function as "sliders" in case of a dump. When I got punted by an SUV at a stoplight a couple of months ago, my left brake lever got broken off because it was the thing that stuck out the farthest when the scoot went down on that side. The bar ends stick out just a bit farther than the brake levers, and I consider them to be "sacrificial".
Besides, they look great!
Just cut out the rubber ends of the grips with a #11 X-acto knife, and drill and tap for a 6mm screw in the center of the mild steel plug. You'll need about 3/8" of spacer on the left side, and about 1/2" on the right to allow the throttle grip to turn freely. Eyeball it carefully and use a center punch to get the hole started accurately in the center, or it will look like shit.