I had the same issues with my KSG......I didn't want an electronic sight, and didn't want iron sights that had to be popped up before using.
Here's what I settled on........
I bought an Archangel Auxiliary sight that mounts to the rail.
The front sight is a bright orange AR-15 sight that's adjustable for elevation.
The rear sight is a simple notch pistol type sight adjustable for windage.
I modified this by making protective "ears" for the rear sight from Kydex plastic.
I made smaller spacers to fit under the ears so that there was enough room to allow some windage adjustment for the sight. I bolted the ears and inner spacers on with black finished hardware store small bolts and lock nuts.
This is dirt simple, requires nothing to ready for use, and works like a standard shotgun sighting setup where you just look over the sights to get a "flash" sight picture, but you can use it for more precise shooting with slugs.
This is as fast as a standard shotgun bead front.
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Do some online shopping for a better price.
Another option is a non-electronic sight that bolts to the rail and is a complete sight in a single short package.
A number of KSG owners have bought the Seeall sight.
This is small and uses no front sight, and is not electronic......
SeeAll Sights
www.seeallopensight.com
Amazon.com : SeeAll The Original Open Sight | Gen-1 Gun Sights | Compatible for Rifle, Shotgun, Pistol | No Battery Required (Standard, Crosshair) : Sports & Outdoors
www.amazon.com