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Here's a Colt Whitetailer missing its factory optic, though it still has the normal sights which a Colt Trooper would feature.
Nothing would stop you from getting a new scope or other optic and putting it on there, presumably a modern red dot would be the most practical choice. Of course, you wouldn't have those scope rings with built in iron sights. Don't know if those are commonly available, I've never seen this on other scoped revolvers, and don't know if something like this is even an available product otherwise.
Or you could just do like The Joker, as portrayed by Jack Nicholson, carrying this long revolver inside your waistband.