Pouch -
I printed this in PLA+, but I can't see why any material wouldn't work just as well.
There are 4 wall's and 10% infill and I printed at a 2mm layer height. My printer is very well dialled in. I want to highlight this as the clasp is a one print design at this time. (I may revisit this later to add in a 3mm rod bar replacement with separate clasp piece, It would work like the hinge section below)
I used supports, but it should only need it for the front bar and the hinge holes as I like to try and save plastic if possible.

There are two version's.
One with a molle attachment that's designed for standard belts like the one pictured.
One has a belt loop for a normal belt.

The pictured pouches are my printed prototypes so please ignore the issues you'll see (I love the amount of P's in the last sentence), with the findings from the prints built into the files shared (I'll be reprinting at some point). These alterations include a stronger clasp with added section for easier opening. Also reinforced hinges, with a 4.2mm diameter hole for the rod.

I'll used 4mm threaded rod as the bar in the hinge, I had this already and wanted to use it. You could print off a circular bar at 4mm for a completely metal free design. The length of the bar I used was approximately 65mm.

To seal the hinge bar in place I used UV resin. After making sure the bar was as close to centre as I could get it I dripped the UV resin in place and cured it. Alternatively you could PLA weld the opening closed, or extend the bar out each side and add on a locking nut, for a different look. (Yes, I could have added a print in place hinge, but no matter what way I tried this I ended up using a lot more filament in supports, and that costs money and whilst I like Batman, I don't have his cash.)

You may see areas such as the molle sections on the printed pics that are smooth. I coated these in 3d printer resin, cured and sanded. I've also found this a good way to reinforce any part, as well as an easy way to get a smooth finish if needed.

Spacer -
Same printer specs as above.
Like the pouches there are the two versions, one for the belt as pictured and one with the normal sized belt loop.
These are designed to look a little similar to the unused sections as seen on the Batman belt design, from the Nolan trilogy. (I just didn't want the plain black belt showing through as much.)

The molle version slides onto the pictured belt with a bit of wiggling.

If I had access to some seriously good bar neodymium magnets I'd trade out the raised sections, and add magnets to the spacers and the pouches to allow a fully modular belt system. (would love to do this one day.)

General thought / notes -
The initial fit was snug, where the top slides over the bottom half. A bit of sanding eased this.
I added more thickness to the clasp, as well as a small section to allow a finger to better open the clasp once shut. As mentioned above this is based off the findings from the prototypes. I've not been able to reprint as yet due to another project needing my attention.
So if you do print off and find an issue, let me know for future designs.
These are fairly solid prints, I wanted them to be able to stand up to a few knocks.

External dimensions at widest point appox-
Width = 75mm
Height = 127mm
Depth = 50mm

Internal space Dimensions approx-
Width = 65mm
Height = 109mm (119mm to top of the pouch when closed).
Depth = 30mm