Ideas needed for a project on an online marketplace for sustainable clothing.

I have this project to create a clothing marketplace similar ASOS, but will only promote brands using sustainable or echo friendly materials.

We are 50% completion if the project and my question are 1. We also proposed on supporting a few charity organisations, but having difficulties on selection

1. How do I go about advertising this project to potential vendors?

2. Will offering the first 200 vendors, no fees for a year be good enough to bring them onboard?

Please if you are interested in such an initiative please comment or PM.