Yes, they have dpns in size 11, but you might not want to buy a set just to use for cables if you don't think you'll use them otherwise. A cable needle set would be better if you're going to buy something, you can use it more. But if you have size 10 or 10.5 in a regular needle you can use it, or a crochet hook, or pen/pencil. Just anything short and straight you already have will work.
sue- knitting heretic