Your model of paying for divulgation doesn't solve the free rider problem.
Still, lighthouses can be run profitably in a voluntary market so there is no reason that this can't.
Only difference is that it's likely to be less profitable than the paying for diffusion model (back when it used to work). You will never be able to completely eliminate free riders.
I'm not sure that free riders are an issue as long as the seller can make sure he raised the expected amount of money.
If you buy a car, and then lend it to a friend, I'm not sure your friend can be considered as a "free rider". Once your car is bought, you can share it with someone else : it's not the initial seller's business anymore. Selling divulgation allows alienation, while selling diffusion doesn't.
Indeed, it's likely to be less profitable, of course. But since sellers presently use public force to sell, I can understand that they make more money than if they wouldn't. A gangster certainly makes less money with no gun.