25+ years ago there was a place that would drill out and retrofit tritium vials into fixed sights but I don't remember the name. If yours are fixed sights there may not be a lot of options. Older sidearms, especially wheelguns, were designed before lasers, night sights, optics and lights became fairly common. If your sights are dovetailed in then you probably have some options.

If a laser interests you at all then there are grips that have the laser mounted inside. I'm not big on lasers but a buddy of mine has a RDS and laser on his Beretta APX and it does seem to work well.