I have been using a military surplus West German combat knife. Very thick blade stainless, unbreakable, Metal scabbard with belt frog. Cost me $45 and never needed to sharpen yet and never once shown any rust.
They look like this (not my image):
http://www.samilitaria.com/SAM/Trade...knife%201a.JPG
Prices have gone nuts on them but I know there may be more, cheap enough