I recommend this protein ampoule (purchased with my own money, 10 times)

The product I am using is Hair Plus's Protein Bond Ampoule.

It contains protein, so you can keep your hair more moisturized.

There is a larger size available, but I purchased the small size for easy portability and am currently using it.

I use the large size at home, and after exercising and showering, I carry the small size around to use.