I have gastropareis and have to rely on smoothies for most of my nutrition. I bought two books - Living with Gastroparesis by Crystal Saltrelli and Healing Smoothies by Daniella Chace, MSc, CN.
The Living with Gastroparesis book has a few smoothie recipes and teaches you how to make your own almond milk.
The Healing Smoothies book is available on Amazon and it's actually focused on nutritional support for cancer patients and preventing cancer. The smoothie ingredients recommended in the book have been clinically tested. The author tells you what each ingredient does. I read if front to back and there is so much good information and recipes for smoothies, teas, and juices. Since you have gastroparesis you might have to decrease the fruit measurements in half so you aren't getting too much fiber.
Here's the Amazon link for the book: https://www.amazon.com/Healing-Smoothies-Research-Based-Delicious-Prevention/dp/1632204479