I ride reflectorized (the best defense is offensive attire).
When I stick my hand out to signal, it isn't. So I took a small strip of reflectorized material, cut it to size, and stuck it on the tabs of my fashionably retro-grouch cycling gloves. Now when I stick my hand out, up, or down in low light conditions, the back of my hand is illuminated by the lights of any vehicles coming up behind me.
Why don't glove manufacturers do this? Or do they, and I don't know it?