Hey pl, ZooMed makes the 100% cypress mulch as does All living things. All living things makes a twice milled 100% cypress mulch which is top of the line. Steer clear of the "blended mulches" bc they contain other undesirable ingredients.
Colin Weaver has written extensively on the benefits of using cypress mulch for poor feeding and non feeding ball pythons. His methods are proven and he has various articles on different topics as well. His case based reporting of non feeding ball pythons is very interesting and a must read. I have taken a page or two out of his book and had nothing but success. Switching substrates once the animal is feeding on cypress mulch can be problematic. "The enigmatic ball python appetite" is the title of this article. One of many.