You searched for: “espousers
espouser (s) (noun), espousers (pl)
Someone who advocates or supports beliefs or procedures: The owner of the company Joyce is working for is an espouser of equal pay for both women and men.

Quite often, an espouser is someone who "marries" an idea, or principle, and embraces it as his or her own.

There are also espousers who join others in conservation or other environmental causes which need attention for better living conditions for humans and other creatures.