Someone mentioned the kabar dozier folder. I think there are two different lines of kabar doziers. The lower cost folders can be gotten for under $20, including shipping, on ebay. They are good, lightweight (2oz), lockback knives. you can spend a lot more money for less knife. It's what I use when camping/hiking in the northeast.
This is the one I was referring to:
http://www.knifesupplycompany.com/kb4070.htmlIts not the 'lower' cost one, but a nice large-ish lock blade that doesn't take up too much room. Blade is beefy and you can baton with it with no worries to the blade.
It sits in my large psk and is my backup knife ("3 is 2, which is only 1" theory).