Jobs at small Omaha companies nobody posts about after 10 years as a bookkeeper

Two small Omaha employers told me they are hiring but have not posted yet. It has been weighing on me all week. One is a print shop, one is an accounting firm and one is a clinic. 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.