For a more portable field kit, I can recommend the AG Russell Field Sharpener rig.

It has a pair of diamond rods and a pair of 400 grit brown ceramic rods. These are 4 inches long and 1/4 inch in diameter.

The angle is 15 degrees (30 degrees compound) which corresponds to the "back-bevel" slots on the sharpmaker. If you keep your knives that sharp you're set. Otherwise, you can put the final touch on the 20 degree (40 degree compound) edge freehand.

Bear