Hi James,
I wouldn't worry as much about finding the "Big Guns". Chances are, if you're what they are looking for, they will find you... usually by word of mouth or maybe meeting you at a marketing seminar.
It's been my experience that many times, there's people at the event as attendees who are making more money than some of the speakers. They just choose to stay out of the guru limelight.
Your portfolio is one of your biggest tool for getting clients. Focus on adding pieces to it and removing your previous efforts that did not perform as well.
Don't be in a rush to get to $5K, $10K, or higher in fees until you have the skills and expertise to justify those types of prices. The types of clients who will pay $5K and up are already pretty savvy marketers themselves. They may be fairly good at writing copy as well.
You aren't going to be able to "fake it until you make it" with them.
The more you charge, the higher the stakes to deliver good or even great copy.
At the risk of hurting your feelings, I would suggest you work on building stronger marketing skills.
If you aren't sure how to reach your ideal prospects... that's a marketing issue.
If you aren't sure what makes them buy... that's a marketing issue.
Solve these marketing issues and you will have plenty of qualified prospects coming your way.
Hope that helps,
Mike