By keeping it in your survival vest, I am assuming it won't be your everyday carry. If your looking for a moderately priced, good quality knife you can stash away and not worry about...I'd get the Buck Hunter, the Buck CrossLock, or maybe a Buck Alpha Hunter in ATS-34.
If you want to go really cheap, Brigade Quartermasters has Smith & Wesson Cuttin' Horse knives available for around $10 each. Get two and stash 'em in there. You could use one for a spear, and one for food prep, etc.
Hope that helps! I know choosing a knife can be a PITA, that's probably why I have tons of knives around and a low bank account balance. <img src="images/graemlins/smirk.gif" alt="" />
John McIntire