designer for non-profit project

Alternatively, you can try on freelance exchanges to look for beginner freelancers to develop portfolio "for review" (if not prohibited by the rules of the exchange) or the minimum amount.

In such a situation would have to be not a buyer of labour and a seller. Think about bonuses of your project for the designer and try to "sell" him the opportunity to participate. Advertising project you can safely hang on freelance sites or look through the Google studios that participate in such projects for demonstracii social responsibility of business.