Grab a pair of pliers and a sturdy rubber band. Wrap it a couple of times around the handles and voilá!
The holding angle might be somewhat more limited than those purpose-built tools. On the other hand, thanks to their higher weight, I find the pliers to be steadier and to provide a firmer grip. You can pile them up to some extent too, to change the angle
(The purpose-built helping hands image by joebeone, used under CC BY 2.0)