Any mass gainer shake is going to be full of low quality carbohydrates and oils as fillers. It is pretty much a sure way to get fat.
Your best option is to make your own high calorie shake. It'll be much cheaper, and provide much more nutrients then any mass gainer type of shake.
Buy a high quality blender and blend together the following:
2 scoops of a high quality protein powder such as wheytobuildmuscle from n2bm.com
http://needtobuildmuscle.com/store/P...scle-p290.html
oatmeal
natural almond butter or peanut butter
frozen fruit
banana
ice
chia/flax seeds
spinach/kale
You can easily make the shake 800 calories and drink it for breakfast.