I use this stuff, it absorbs wastes well and last me a loooong time. I used to use paper towels but between cleaning and substrate it was becoming quite costly. I was a little concerned when I first got it because it appeared a little rough but I didn't notice any irritation on the bellies of the snakes after a couple weeks so I've been using it since. I also want to try out the non-intented version to see which one is better.
http://www.uline.com/BL_1961/Indented-Kraft-Paper