If you really don't want to buy protein powder, you could probably substitute with Carnation Instant Breakfast.
Also, if you find yourself liking these as much as I do, you may want to invest in a good blender. I just spent $80 on a good blender that was WELL WORTH IT.
I'm sorry, but the protein shakes recipes have been moved to my everyday blog, Runs for Cookies. Here is a direct link to the protein shakes recipes.