Any 'weight gainer' or 'mass gainer' type shake is going to be full of empty calories. Particularly simple carbohydrates and low quality oils - usually sunflower and soy.
You can make your own high calorie shake very easily. It'll be higher in macronutrients, micronutrients and be cheaper. It's a better option all around.
Buy a high quality blender and blend together the following:
2 scoops of a high quality whey isolate (I like isolation from n2bm.com or a whey isolate from truenutrition.com using the natural flavouring option. Both products are sweetened with stevia and only use natural flavours. Use code tkz564 to save 5% at true nutrition)
ice
frozen berries and/or banana
oatmeal
natural almond butter or peanut butter
flax seeds/chia seeds
spinach/kale/other dark green vegetables
Drink haft before your workout and haft after.