For a mess tin kit, I like to go with a SAK. Big enough to do most things with, you have a number of options with a saw, and you get to have something big enough to hang onto.

Baring that, there are a ton of options. The Hibben throwers (the older ones) in the small size, if you can get a good edge on them might work in your size restrictions. The Aitor Skinner II is a classic, when you can find them. There are a number of other, "skeletonized" knives out there, particularly "neck knives" that would work well in a mess tin. The Becker Necker might be a little big, but Boker has one that might work, I can't remember it's name right now.

If you look around, particularly at ren faires, you can find a custom smith who will make you what you want for a decent price.

UPDATE: The Boker model is the Magnum Escape. Very reasonably priced, under $20 if you look around. You might also check out the Spyderco "Spot", it is very similiar to the second sketch you posted.