You could probably also use a short heat cable. I think the one we have is made by Zoo Med. Ours is fifteen or twenty feet I believe. You can use it under the cage or inside it and the first few feet near the plug are cold so that's a nice extra. I have it wrapped around the two dowel rods in my home built cage I have my two jungle carpets in. It works pretty good. I believe it is available in different lengths, for various sized caging. Hope this helped.

Daniel