Bivy Sack: Similar to the thermal blanket, but even better, the bivy sack will keep you snug, warm and dry while you sleep.
Lures and Line: Carrying a pole is out of the question, but you can pack fishing line and lures for some ice fishing. It could save your life.
Pack Sled: How do I carry this, you ask? Take along a small pack sled you can pull behind you. It'll save you having to add 50 extra pounds to your pack.
Snow Shoes: While they may look ridiculous, these babies can be the difference of you walking to safety or getting stuck in the snow and freezing to death.
5.11 Tactical Pouch: This small pouch is durable and can fit a lot of survival gear. As a bonus, it can hook to the outside of your carry-on to save you some space.
Stone Arrowheads: You can pick these up online and with some thread and sticks, make great hunting and defense companions. But a word of caution - be smart about the size of the ones you try and put in your carry-on.