If so, why can you not make one out of a wire coat hanger?
I've been thinking about the same thing, but I'm not sure a wire coat hanger would be stout enough. It would probably bend and distort if you tighten the belt even a little, or if you try to hang any weight from the belt.

I've had good luck in the past using 1/8" diameter steel rod, which you can usually find at any hardware store. I've even made custom roller buckles from 1/8" rod stock when I couldn't find a buckle to fit my need. As an example, I was building a replica rifle sling for a WWII-era Russian rifle, and simply could not find a buckle that looked like the original. So I bent some 1/8" rod and made my own, then cold-blued it. It's the one on the left:



The 1/8" diameter steel rod should be plenty stout enough for a kilt belt waistplate connector, and it should be easy enough to bend into shape. Especially if you make yourself a wood block as a bending jig. Then just scrub it with some steel wool, degrease it, and cold-blue it (unless you have access to chrome or nickel plating equipment). It should work like a champ!

If I ever get around to making the custom tooled kilt belt I've been talking about, this is what I'm going to have to do for the waistplate connector. Maybe if I do that, I'll build several of them for the rabble here that need them. But it likely won't be anytime soon.

Why don't the regular kilt accessory vendors carry these??????????