I don't mind knitting I-cord but it is a rather time consuming when I need a long piece for a hoodie tie. I bought this from Bond America at http://www.bond-america.com/products/embellish-knit.html.
This handy device cranks (literally) out I-cord quickly and easily. The package says it can be ideally used with the following yarns: Baby yarn, embroidery floss, cotton crochet thread, sport yarn, metallic yarns and floss, lightweight fancy yarns and lightweight chenille. I tested it (see attachment) and found it most satisfactory. For this test I used the acrylic yarn sample enclosed in the kit.
This is a very useful device to have around. I thought you might want to have a look at it in case it's unknown to you. I learned about it from a knitting blog.