Have you considered just buying a knife with one of the new high hardness, high toughness steels and forgetting about the sharpener? I have a Tim Olt M4 blade that I cannot imagine getting dull on one hunting trip. I have a number of VG-10 blades that are very similar. You could just drop the knife by a shop to get it sharpened should you get it dull.
It doesn't make up for not being able to use a sharpening stone, but it is a work around that more people use than not.
