I was going to ask the same question - maybe tritium sights. The indoor range has very poor lighting and all you can see is a silhouette of the front sight alligning with the rear sight and that is only after moving the sights off the black for a second.
Well I contacted Trijicon and PT Night Sights and they both had the same response. We don't make sights for the P22 and don't have any plans for doing so. You can contact our service dept about custom installations. I guess they figure there isn't a market for it.