There's a terrific book on Calder's life called "Calder" by Jed Perl. In the book is a couple of photos of Calder posed with his favorite wire bending tool - a pair of Bernard Pliers.
Many times when I've made my own stabiles and mobiles I often think about what tools Calder used to make his own. On a lark and for fun I logged into eBay and much to my surprise and enjoyment when I searched for the same brand of pliers I came across dozens of offerings. Matching the design/look from the ad in the Perl book I bought a pair for around thirty bucks.
I can see why Calder liked them so much! They feel great in ones hand and are just the right weight and size. They grip metal rod and wire really well and also have this nifty wire cutter on the top. I especaillly like the way they look. When the jaws are open they look like a Gecko lizard with its mouth open!