Jobs at small Milwaukee companies nobody posts about - 13 weeks in

A friend who works at a local manufacturer says there are openings not advertised online. I have read a lot of threads here and could not find my exact situation. They prefer people who can start within a couple of weeks. What do you write in a cold email?

A short email with two sentences about what you can do and your résumé attached worked for me. I followed up after a week.