I've made them before with wire I bought in the fishing section at Academy. The trick is to get some that is both flexible, but also has "memory" so it won't open back up if they go in the opposite direction.
I know that's probably not much help, but I've had some success.
On a scary note, apparently an extremely large hog got into one of mine that I set. The tree it was anchored to was completely shredded and the wire (250 lb) was completely blown up.