Yes, available at my local auto parts store. And yes, they are big and heavy compared to almost every other form of fire lighting. But, if you are shivering from hypothermia, small things may be impossible to manipulate. Big things are easier. If you have never lit a road flare, I suggest you try one (in an area with no burnable materials). It produces lots of very hot fire with very little trouble. Remember to strike away from you, hold the flare away from you, and do not let it drip on you. A 5-minute flare is about 5-inches long. You may be thinking of 20 or 30-minute flares (more common), that are about a foot to 18-inches long.

Also, as I stated before, this is my last ditch, must make fire NOW or die firestarter. My usual firestarter when backpacking or camping is a match. As my father taught me (under non-survival situations), "if a man cannot start a fire with a single match, he does not know how to start a fire."