I had no idea what FHIR is. I googled. I followed about five or six links without backing up to land here: http://www.hl7.org/about/gold.cfm?ref=nav

Start cold calling. Collect names. Fill a rollodex. Don't stop. Fill another. Follow up in person.

Ask about what's in their current budget. What's coming down the pipeline. How they currently handle work in your area. See their physical infrastructure. Know what the decision maker's office looks like. Get a sense of their actual problems and assure them that you can mitigate them.

Get your ass to work. Out of the chair. In the car and cheap motels. Stop pretending there are clients on Hacker News. There aren't. It's just easier to post here than cold call.

Good luck.