I've been grabbing those Bolthouse Farms shakes at work, but they're 1) expensive and 2) not vegan, and I'd like to start getting closer to vegan again. Those shakes do have a really nice thick creamy texture. They're whey + soy protein, probably some other thickeners to achieve the consistency.
What I sometimes mix up at home is almond milk, Genisoy protein powder (don't believe the weirdos on Amazon who mix this with plain water - it tastes like nothing), and Ovaltine (for vitamins & flavor; but it's ONE ingredient away from vegan, which bugs me). This tastes good, is pretty cheap, and can be made easily with my blender shaker ball thing, it just lacks the thickness and variety of the premade shakes. I've read about chia/flax for thickening beverages - but how do you separate out the solids once they've done their trick?
I'm almost out of Genisoy and ready for new ideas before I buy anything again. I could maybe get an actual electric blender soon, but I'm a last-minute person, often mixing my shakes on the way to my car, so simpler = better.