Member-owned co-ops like credit unions and REI come to mind. They follow a "one member, one vote" rule. Credit unions are not-for-profit, while REI makes billions in revenue, and both provide great service. They're an existence proof that it's possible to still be a good business while governed democratically.

In some countries like Finland, the democratic government holds some large non-majority stake in companies that affect the public interest. However, I don't think that model would work in the US, particularly in light of some unique jurisprudence (Buckley v. Valeo, Citizens United v. FEC, and Americans for Prosperity v. Bonta) that make all three branches of government captive institutions to a small number of wealthy donors.