ReferenceUSA will be helpful for finding individual businesses in an area such as grocers or farmers. When you log in, click on US Businesses, then choose Advanced Search. On the left side, choose Keyword/SIC/NAICS and from there you can search for keywords such as vegetables, fruit, etc.
IBISWorld gives us industry reports. This will be helpful for getting a broad overview of supply chains, markets, key statistics, and such for an entire industry. We might try to search on the main page once we sign in for vegetable or fruit and then view the reports for Fruit & Vegetable Wholesaling in the US, Vegetable Farming in the US, or Fruit & Vegetable Markets in the US.
These article databases will be helpful for finding information in trade publications and scholarly publications on supply chain management for the food industry, articles about nonprofits who may have tried similar projects to ours, and more.