How to acquire data on US listed exporting firms?

Are you aware that list may include 90-95% of the US corporations?

Have you tried a public library? I think that what you're looking for might be hard to come up with. However a good librarian might assist you best.

In what country are you located?

You're trying for a Masters degree and you haven't looked into using the university library? A college or university library would likely have several related database subscriptions (a bigger reference budget then smaller public libraries). If you live in a relatively big city, the main research branch of said public library should be able to help.

Unless <gasp> this is some ruse for a spam attempt?