Forum member, sixshot, sells these that, I believe, his son makes. I bought 2, one for me and one for a friend. The quality is excellent! I havn't used mine, but I shot my friend's Single Six with one and liked it. It was the 7/32 sized (smaller one) IIRC.
I've put them on all of my Ruger single actions and haven't looked back. You won't get the fine sighting good eyes will get with a nice set of adjustables. Those get real fuzzy as you get older and the ORH is plenty good enough for day to day shooting.