Get Grade A produce?
Given that US produce grading is voluntary (see:http://www.ams.usda.gov/grades-standards/vegetables), I think your task of sourcing the highest quality produce would be one of searching, asking around...basically trial and error. It, of course, depends on how you define quality (as the comments above suggest).  If it is perfect cosmetic appearance, then yes, large commercial farms are the way to go.  If perfect is flavor, then perhaps small producers specializing in specific crops might be the way to go.