I have a "Supersprox" rear sprocket on my Ducati. These are US made, just FYI.
These sprockets have a steel "ring" riveted to an aluminum alloy hub, so will last as long as any quality steel sprocket, while being almost as light as an all aluminum one.
They now offer "custom" sprockets, made to individual specs, but these cost a bit, around $100. The minimum number of teeth is 36, so is a bit big for an XS, but may still work fine, depending on type of riding, front sprocket size, wheel size and any primary gear/ fifth gear ratio modifications. (I believe Heiden Tuning/ Mikes XS offer these mods)
On a stock XS rear hub, the weight savings from a "Supersprox" sprocket may be neglible, due to the small sprocket and big ID. On other hubs, like my Ducati, the weight saving may be close to 1 Lb.
For a stock XS hub, an optimally designed/machined steel sprocket may be almost as light as an aluminum one. I went from OEM 530 to a 520 steel sprocket from Heiden, and lost around 10 OZ.
Anyway, just google "supersprox"
Good luck!