ESG Valuation

I have to show how much ESG factors impact the share price of a listed company. It is a hard analysis! I need good assumptions to use in my analysis. I would like someone to tell me how much in percentage terms the cost of capital will decrease as a result of good ESG practices. I need to know where the % comes from (and it needs to come from a reliable source) so I can use it in my analysis. If anyone knows how to do this differently, I am also open to suggestions. I need this by tomorrow afternoon (Sydney Time)