Here are three ideas:
1. Find the person who is in charge of the area of the company where you want to work. You can use LinkedIn for that. And contact the person. Let them know you want to work with them and ask them to keep you in mind. Then email periodically to check in so you stay on their radar. You can also email them with an updated resume if your resume changes while you’re waiting. It’s good to say, “I just want you to know about this recent accomplishment… and I’m still looking forward to interviewing with you when the time is right for the company.” Something like that.
2. Send an email that is essentially a pitch to do consulting. Show them that they need you to solve a problem they didn’t know they had, or they didn’t realize would be easy to solve – by hiring you. You can start as a consultant and get them to hire you full-time later, or you can convince them in the interview that it’s a full-time position.
3. Work for free at the beginning. At a very small company there is often a need to hire someone before there is money to hire them. If you get a foot in the door before there is money, and you do a good job, then when there’s money the job will already be yours. And bonus: you’ll get extra stock options for working for free.