My traveling sewing kit is just like my stay at home kit - after leaving home without some good scissors - I bought a new set of scissors to keep with my traveling machine. Heck, I even carry an extra light bulb for my sewing machine. One time I failed to have any sewing machine oil and to get some I had to buy a kit - and in the kit was a light bulb for my machine. And on one of our sewing trips to Vegas my friend's light burned out. My daughter said I might have one, and she thought "No way" but there is was! Now I just keep the one for my FW, I had bought an LED bulb so the old one is in the box.
I keep a granola bar in mine too because when sewing I sometimes forget to eat on time and my blood sugar drops and I am shaking before I realize it.