I've never found anything I really like. One of my thoughts was to start with the Gatco Micro-X Pocket Sharpener:



which is $8.99 from Campmor.com. It has a pair of fine and medium grit sticks, which is nice, but it has a fixed 45 degree angle (22.5 on each side). Since I use Ritter knives which have 30 degree grinds (15 on each side) I don't care to use that preset angle.

So, I've always thought about taking a reeeal small block of very hard wood (oak?) and drill out my own holes at the right angle so it looks something like a Sharpmaker.

I figure I could also then drill four storage holes in the ends. I'd have to be careful about not slicing a finger since I probably wouldn't add a hand guard.