If you feel that your agent isn't performing to your expectations, engage in an open conversation with them explaining what you feel isn't being done. Refer to the services spelled out in the contract. It's possible that miscommunication is the problem, and tour listing agent should get the opportunity to make it right. If you still don't see results, talk to other brokers at the firm carrying your listing and see if they can meet your needs.
You can also look to certain companies and organizations that have a concentration of people that may fall in the above mentioned roles such as investment companies (i.e. Charles Schwab, Fidelity), financial advising companies (i.e. Morgan Stanley, Merrill Lynch). There may be a higher concentration of people who can both afford and want to build their own custom homes or to build income-producing properties. Try linking yourself to financial advisors who may already know of people who have these types of dreams. This isn't a comprehensive answer of all the possibilities but just some thoughts. Good luck!