I bought a Mora Garberg from TBS and chose the option for having a leather sheath with it which i believe they sell separately. It fits their leather sheath great though it does have a folding closed flap with a press stud that im not overly keen on.
You might try soaking the sheath in warm water until it softens, then put the knife, greased and wrapped with cling film, into the sheath while the sheath dries, having formed the sheath to the contours of the knife with your fingers. It will then take the shape of the knife. Will need a good polish once fully dried.