You actually don't need to get a slanting stool. A slanting pillow works just as well. I also think it would be more comfortable, or a chair with a back that you can adjust to a slant. Those stools look really uncomfortable, but I could be wrong. Anyway, I am very happy to hear that you are much better now.
Here's a link to what I got. I also got an adjustable chair from an office supply store.