A traditional sgian is meant to be worn in the sock, so I assume we're taking some leeway with not only the carry style, but perhaps knife design as well. If you consider having a custom sheath made it opens up a lot more possibilities for sgians that don't come with a belt sheath because they are intended for use with kilt hose...

You could look at the Cold Steel Secret Edge, which has a neck sheath and wouldn't ruin any vehicle seats
http://www.coldsteel.com/Product/11SDT/SECRET_EDGE.aspx


Or the slightly more expensive one made by Atificum Solice. It comes with a sheath, but they don't show a picture of it.
http://www.artificumsolis.com/Produc...ode=Sgian-Dubh