The easiest way that I can think of would be to head to your local hobby lobby and pick up a roll of vegetable tanned leather, a punch, and a rivet setter and some eyes and some mounting hardware (measure your sheath and the thickness of the leather for sizing)
- Cut a length of paper to size as an approximate and mark your holes on one side, punch them and set your eyes.
- Mount that onto the sheath and thread the leather strip behind your belt and size the loop to your liking and mark the leather at the underside of the sheath, so you will have a reference point when off of the belt.
- Line up your mark with the underside of the sheath and mark a line to show how much loop is needed above and make the sheath to line up the strap.
- Undo the side that is attached, line up the leather as per your marks, and mark the holes to be punched on the other side.
- Redo the previous steps for setting the eyes and mount your new belt loop.
You should have plenty left from the roll to practice your tooling and can now spend some time making a fancier version.
Good luck and post pics
