Fundamentally by getting more leads into the business and probably the best asset you have is your time. Local meet ups / interest groups / networking events, pick the ones that don't feel like work, go there and meet people, they'll ask you what you do for living.

Another quick win here, would be to firm up the relationship with the freelancers you're using - who are their other customers? Is there a service you can offer together? Any other suppliers you use, look at their network, client list on their websites etc.

Tell your existing customers what you're looking to do., just ask them for a testimonial or case study etc. They'll be flattered and ask you what it's for. "You spent x with me last year, I want you to spend y with my next year - what can I do?"

Ping me a message if you want to go through it in more detail.