Rice protein powders are usually very tolerable, and if you are used to beans/legumes soy protein can be tolerable as well. I would be cautious with pea protein powder, and definitely avoid whey completely, as well as any other protein powder with dairy.
Powdered egg whites would also be a safe powdered protein you could add to drinks.
I don't know of any commercial protein liquid drinks that would be safe for IBS. It would be best to make your own drink or smoothie with the protein powder, a non dairy milk, and ideally some soluble fiber from bananas or even a handful of oatmeal thrown into the blender.