Kydex? Nylon? What are those?
Kydex is a newer blended material acrylic / pvc many commercial holsters are made of it today long wearing and tough but definitely not traditional
they did have metal spring clips back kn the 1800's so a spring clip to boot would be acceptable
some were sewn in, some used a lace through side of boot, most were strapped to the calf
So it's your choice how you would like to go.
Mike does good work He's down in Colorado