I use the Pure Protein powder in Frosty chocolate. It's only 140 calories, 3 carbs, 25 grams of protein. It's not too sweet and it is very reasonable, I buy it at Walmart for under $20 for a big tub. I don't put it in the blender it gets too frothy - I mix it with water and put the shaker bottle in the freezer until it's really cold almost crystalized.
The ready to drink Premier Protein from Costco and Sams Club is also very good - and about $25 for 18 cartons, 150 calories, 5 carbs and 30 grams of protein.