I decided to run a simple cable down the center of the sock. The only problem was, I didn't have my cable needle with me. I thought the yarn might be stiff enough, or the stitches big enough (size 2 needles) to just take two stitches off the needle and let them sit there while I knit the next two stitches, but that didn't work well for me. So, here was my solution:
Here is the completed sock (a long sock for a long trip):
I liked this method so much, I may never use my cable needle again. I doubt I was the first person to do this, but it was a new idea for me. Maybe you will like this trick, too.