Making ear wires on the fly can be accomplished with just a few items, my kit contains 5 items. It is the basic kit and will get the ear wires into a basic shape, that can be refined in the studio as needed.
My kit contains wire, I use 19g half hard wire. This wire makes for a sturdy and durable ear wire. A ruler, flush cutters, cup bur also known as a wire rounder (sized to fit 20g wire, .8mm) and a pair of my favorite round nose pliers from Eurotool Acculoop round nose pliers.
You can also use a pair of round nose pliers and a pair of bale making pliers but my goal here was as few tools as I could get away with.