Annealed steel wire comes in packages in your local hardware store. It's important to run your working lengths through steel wool to take off any oil or coating out of the package. Steel wire is super hard and will damage your good wire cutters, your good hammers and your good bench block. Use old tools when working with steel and save your good stuff for non-ferrous metals.
Xuron heavy duty cutters cut through annealed steel wire with ease. Be careful not to use your fine flush cutters on steel.