At the Institute H21 symposium last week in Prague, Stein Ringen described his proposal for a campaign finance clearinghouse. I gather Ringen also defends this idea in _How Democracies Live_ (Chicago, 2022)
The idea is that you could give money (up to the legal limit) to candidates, but you would have to make your contributions through a clearinghouse that would transmit the funds to your chosen recipients without telling them who gave them the money.