Have a Fallkniven Garm, I think they call it. Kydex sheath. Could use my WM-1 as a neck knife, I guess.
Oh: I have an old knife with plastic sheath from A.G. Russell. Very sharp, and light on a neck cord. Quite small, but could be very useful if I surprise an opponent with it.
I've seldom worn neck or boot knives unless a particular circumstance warranted it.
To see the Garm and other fine knives:
{:sv}Fällkniven - Quality Knives Sweden{:}{:en}Fällkniven - Quality Knives Sweden{:}
Don't panic at the prices; they 're in Swedish kroner/crowns. Yes, the knives are worth the money, although they aren't cheap even in US funds. Check out the Northern Lights series, with leather handles.
You don't have to import the knives. They have US dealers.