Ask HN: How to find contacts of decisions makers for startup sales activity?

I am a co-founder of a startup. We have launched a product for e-commerce and travel category. I am wondering how can I find contact details (mainly emails) of decision makers?

I will be mostly reaching to CEOs, CTOs, VP of Tech who have buying power. These will be small and medium size businesses. I am not targeting enterprise customers at this time.

Any help?