I would imagine the reason you don't see premade sheath options online much, is because of whole handle, or lack thereof, deal. Most good Kydex or Leather sheaths at least cover a part of the handle, and that makes up an integral part of the fit. However, nobody knows how you handled your knife, unless you hand it over to them, which isn't cost or time effective. Do you have yours wrapped in paracord? Two layers of cord? Big bulky burl handle for cutting comfort? Thin micarta for carrying comfort? etc...
That's part of the fun of the mules, though. I plan on picking up some leather this week and having a go at it myself.