That isn't the problem- if we just tell you what to buy, you will also need to know how to install, how to setup, how to clean, how to leak test, etc.
What is your budget?
What do you want to cool?
What idle and load temperatures are you seeing now with the H100 that make you think it's not adequate?
Is the CPU at stock speeds or overclocked?
If overclocked, what speeds and voltage?
These concepts are all covered in the watercooling sticky. Please read through as much as you can as it will still likely help you understand some of these questions and others. This will greatly help us explain once you understand more about these concepts.