Noureen any small Pilates ball should work. You may want to inflate or it deflate it to your liking. About 9" should work. I personally like this one - https://www.optp.com/Soft-Gym-Overball
Carrie Pages probably one of my favorite workouts yet, girl!!! I was riding that struggle bus! And can we talk about the knee pull with rotation? You’re amazing, Carrie girl. Love ya!