Hi:
I was searching for sites that had reviews on the Ruger single six, and came across your posting on this site looking for a holster for the Ruger MKIII. I just had that question myself as I put a red dot scope on my MKIII. I did a lot of searching but found no holster made for that, but then, thinking more broadly, I recalled that I had a holster in my truck that might work. I work as a carpenter and have a holster for my cordless drill. I went and tried it on the scoped Ruger MKIII and yes, it works. :lol: The nicest cordless drill holster that I have found that fits this scoped gun is the one made by Occidental leather, costs $34. But the black nylon one I tried worked as well.
Sooo...try your local hardware store for the holster!
Deb