Holster options are few at this point, red dot or not. Mine fits well in an old shoulder holster made for large single actions and fairly well in a Fobus paddle designed for Berettas and CZs. I intend to cut down the front part of the rail to get a better fit in the Fobus as soon as I get a spare rail from S&W. They're currently unavailable.
I ordered a generic ".22 Auto 5 1/2"" holster made by Blackhawk that fits okay with the irons, but it's really about an inch too long. I may cut the top out to fit the rail once I find some material suitable for re-binding the edges I cut.
The shoulder rig will be fine for field carry as it protects the gun and sight very well.
