Something we carry in our EMA truck are electrical LED emergency road markersGood list guys. I would also recommend carrying extra fluids (oil, transmission fluid, coolant, etc.). This is a good thing to do just for general day to day stuff too. Know how to check all your fluids and how to add more if needed.
Along with the flares, star clusters (I think they're called parachute rocket flares or something in the civilian world) are good if you get lost and are stranded. At the very least it will draw attention that can get you the help you need. They can be seen from the air or ground for miles. If you have a truck and have somewhere to mount it, a hard mount winch is also a good thing to have. Not only for pulling debris from the road, but for pulling other chasers out of the ditch if they get stuck.