There are high-vis light gathering isotope paints for applying to sights. Stores or shops that supply this sort of thing for IPSC and other 'combat-type pistol and revolver shooting may help - I'd try googling for high visibility sights or paint - that sort of thing. As to what I use, a fairly wide rear V and a silver front blade slanted at the rear and polished, or a brass bead, also with a rear slope highly polished for light reflection. I could not bring myself to use the modern slight gathering, light emitting sights, but some do. Even pellet guns today have those 'high-tech-type sights.