(Note: For people outside information security, this comment might seem strange. Some of the jargon used in this industry is needlessly aggressive, and usually ironically so. Please don't be put off by it.)

Exploit the network.

Or put another way: You're working for a company to solve security problems, maintain compliance, identify risk, and prevent disaster. There's potential for a lot of line-of-business grunt work in infosec (especially network security), and there's a risk of being insulated from clients. I've not had to deal with the insulation problem personally, so I'm not qualified to give advice on that (so, I won't).

Hopefully you're in communication with stakeholders within at least one company and most likely with vendors and contractors. Talk to them, find out what their concerns are, inform them of threats they hadn't ever considered, whatever comes natural to you. Find people who want their problems solved but don't know where to begin solving it. Try to move the conversation to lead to being introduced to their colleagues and supervisors.

After a while of doing this, you'll find yourself well-connected to the people in your niche.

This is the recon stage, but in and of itself you can find great leads. While you're doing that, work on specializing your skill set (if you aren't already excellent at something).

You want to be in a position to where your colleagues are your feelers for other companies that want problems solved, and you're the person they ask for advice. These problems don't have to be security related; it could be "We need an Android app for our fleet that streamlines our safety compliance requirements". Seek them out, make yourself available. Coffee dates with other professionals should be part of your daily (or at least weekly) routine.

Blend in, get trusted, establish rapport, be genuine and reliable, deliver value, spread your reputation. Be patient but persistent.

And, of course, there are a lot of general freelancer things that other folks more qualified than myself will tell you about. Read the wiki too, of course. :)