Here is how I make short snap/wire leaders to use when lots of Spanish and Bluefish are around. It takes about a minute to make one with common hand tools and #9-#12 wire. I wouldn't try them on Blue Marlin but they are sufficiently strong for light tackle.(4-20# test line.)
Here is how to make the eye if you want an eye.
Here is how to form the snap.
Snap open/closed
For my own use, I do not make an eye in the top end of the leader. I simply put a tight bend in the end of the wire and tie it to my line with a Bristol Knot. Here are a couple of leaders, one rigged with a Bristol Knot and the other with a formed loop ready for your line.
I start out with 6" of wire to form a 3" leader. Leaders can be as long as you'd like, however.