Uncle has a link to a post about using a computer hard drive magnet as a gun storage device, say on a wall. I found that the magnet is strong enough to use as part of the holding device on a holster.
I started with a piece of aluminum, bent the end over 90 degrees, and installed a 5/16" nylon bolt and nut. This picks up the barrel. I then added the drive magnet to pick up the cylinder of my revolver. The brackets for the magnet keep it from sliding.
The strap is a securing measure as this rig will not allow you to run or engage in other acrobatics without it. It holds the gun well, but it's not perfect.
Note that the red dot is not a problem with this rig. Try finding a leather job for this.
There we go, open carry with no visible means of support. I have since removed the red dot, but the holster is still a fun attention getter at the range. The draw is quick, too.
Note to self: Next time find some curvaceous cutie to model this stuff.