This is a holster idea I've been toying around with. I wanted to try designing a holster that could be almost entirely printed. The only extra parts needed are M4 nuts and bolts.

This holster is designed to be attached to a drop-leg Molle panel.

It involves a side accessory rail bolted to a Nerf blaster(in this case, a kronos), which then has spindles bolted onto the rail, which then slide in and out of a slot in the holster. The fit between the spindles and the slot in the holster is crucial as friction of the slot pinching on the spindles is what holds the blaster in place.

As the 3D printed parts rub on each other the friction will cause the spindles and the slot to wear down. Spindles will wear out faster than the slot in the holster and may need somewhat regular replacement. I don't know how much of a problem this is long term as I've only been able to test this holster at two games so far.

Pros and cons of this holster vs other Nerf holsters available:
Cons
-Requires you to drill holes in the shell of your blaster to mount the attachment rail/spindles.
-The spindles may wear out over time and need replacement.
-The spindles sticking off one side of your blaster isn't the most stylish look. It doesn't bother me but it might bother some people.

Pros
-The holster only occupies one side of the blaster. You're able to attach whatever you want to any other side of the blaster. Sights, flashlights, ammo holders, etc. Go nuts.
-Holster is very low profile while it's not carrying a blaster.
-One size fits all...sort of... As long as you're able to attach the spindles to the side of your blaster, it'll work in this holster.
-Being mostly 3D printed, its cheap.(as long as you have a printer)
-Ambidextrous. No parts need any modification for left or right handed use. Just mount the attachment rail to your preferred side of your blaster.