Alan's cave in Mystery Lake is the easiest place to obtain this. Probably. There is a hunting stand nearby with plenty of twigs nearby - all you need to do is scavenge for genuene firewood early on. Stack up some canned food,. Also, prey in this area might help. Sustain your fire with twigs and woods you find to the north from the cave (it's just there more of them) - it should be enough for 3 days. If not head south to the lake. I recommend not to leave your fire alone for more then 5-6 hours.