I hand made a sheath for my sgian dubh, using a thicker 8oz for the rear with a lighter 4oz at the front. I coated the blade with vaseline ( petroleum jelly) to protect it while wet forming the front of the sheath to the blade and left to dry. The sheath also accepts the first in of the handle.
Yes it's thicker and heavier than the stock sheath sent out wi the sgian dubh, but it sits flat to my leg and stays in place.
If anything, I get greater damage from the garter than the sgian dubh