Tknife, I think a gig is a great idea, but my feelings on this are colored by the fact that I live in a part of the country that has puddles, ponds, lakes, ditches, creeks, and rivers all over the place. Obviously, gigs are generally intended for frogs and fish, but they are just as effective on snakes and small mammals, and might be even on birds if you are quicker than they are, and maybe on small turtles if you are lucky enough to stick some skin.
I agree that packing a gig head in your personal survival kit might not be easy to do, but it's worth considering if there is any way you can put one in your pack or your bug out bag. To complicate things even more, I prefer the gigs that have 5 prongs, rather than those with 3 prongs as shown on Buckshot's Camp's website. Mine has a central prong with 4 more arranged around it in a rectangular pattern. They are mostly straight or parallel when you get them, but I put a slight bend on the outer prongs to spread them out maybe half an inch more at the point. It gives you a little better chance of connecting with something edible. Walmart sells gig heads where I live.
Have you ever heard of a writer on survival subjects named Ragnar Benson?
He discusses gigs at some length in one of his books, but it's been a long time since I read it and I can't remember which book that was in. He was also promoting a design with several prongs (4?) arranged around a central prong, but he had used some that were handmade in Vietnam, Cambodia, Laos, Thailand, or somewhere in that part of the world. From what he said, gigs like that are very highly valued there and greatly add to the quantity of food that a family can obtain.
You may know this already, but gigs are not usually thrown like a spear. They are used to stab or stick with. The idea is to slowly sneak the point down toward your target until you are close, then you use a quick, short jab to stick what you plan to eat. If you are going to stick a fish of any size you will do best to try to pin it to the bottom of shallow water and grab it with your other hand. The barbs on the gig's prongs may not hold in a big fish.