Have you thought about getting one of the belt buckle blanks from Tandy and covering it with the snake. https://www.tandyleather.com/en-usd/home/department/buckles/1800-00.aspx
I don't really like that style of buckle - I prefer the Tandy California style buckles.
A lesson I learned, making these cartridge loops, was using hole punches and wood chisels to cut slots. Turns out, punching a hole at each end of the slot and then using the right size chisel to join them together into a slot let you cut easier and straighter and with more control than using oblong punches. So far, I have never had any good luck with an oblong punch.
For these, I cut a cardboard strip the width of my belt, then laid out the slots and Chicago screw holes by punching each end of each slot and the screw holes with a 1/8" hole punch. The patter goes from one end out to 8 sets of slots. Then I just laid the cardboard on my belt and marked the holes on the back of the belt with a sharpie marker, then flipped the patter around and partly overlapped my marked holes to extend the other end out to the number of loops I wanted and marked the rest of the holes. Then I took my 1/8" punch and punched all the slot ends and a 3/16 or 1/4" and punched the holes for the Chicago screws. All punches from the back side of the belt.
After punching the holes, I turned the belt over and, from the front, took my 3/4" chisel and lined it up with the right edges of the top and bottom holes for each slot and hit it with the hammer and joined the holes, then did the same on the left side of each pair of holes.
After punching the holes and cutting the slots (and re-dyeing the inner edges of the cut slots) I took my strap for making the loops and laced it through, putting a cartridge in each loop, pulling it tight and anchoring it by one Chicago screw at a time, down the row. I would pull each loop tight, then past the Chicago crew holes and up through the first slot for the next loop, then I'd take my 1/8" punch and punch through the middle of the Chicago screw hole in the belt, to make a screw holes in the loop-strap.
Then I set a cartridge where I wanted it to ride on the bet and set my stitching groover even with the rim and cut a groove that the cartridge rim will sit in, to keep them in place in the loops. That's just an idea I came up with while I was working - not really tested yet, but I could feel the cartridges snap into the groove when I put them in the loops. The advantage of the semi-woven loops, over fully woven (1 slot per loop) is that these hold the cartridges against the belt, so it's easier to use something to keep them from sliding down in the loop.
It was a lot faster and easier than stitching the loops, in my opinion. The loops should also be stronger and it's possible to adjust them, or even change the caliber, with a new piece of 3/4" strap. I still think stitched loops probably look better and will give you more rounds on the belt in the same space. The advantage of these loops
I read conflicting recommendations on making the loops with a wet or dry strap. I did it dry. Seems OK so far.