Ever bought your protein powder off amazon? They have a big variety of different brands on discount, for example, 4 lb. MusclePharm Combat Protein Powder, and if you buy two you can get 25% off. One pack will only cost around US$20.41 (about HK$160)!
Additionally, you can also get other supplements for the buy-two-get-25%-off deal!
Shop them via Amazon here: https://amzn.to/2BS1kkC