Underwriters Laboratories is an excellent example of consumer protection in the private sector. As far as I know, no law demands that a product be certified by them, but most savvy consumers will look for that label. The free market at work.

In a free market society, there would be many such companies, acting as checks on each other through competition. Producers would pay to have their stuff certified...maybe even by more than one company if they were enthusiatic.

There is no reason this could not work for many fields where testing is required, including the medical field. The number of such companies (UL, Consumer Reports, other associations) is small under our mixed economy because with the massive array of government regulations in place--whether they really serve the need or not--the demand is small.

Before the rat's nest of government regulations, it was common for private professional associations to be founded that regulated their own industries, and did it quite well. I could reference some histories on this.

The main reason that such solutions are not used or promoted is the same reason that bad government solutions are often used instead of workable private solutions: There is no political power to be had in a private solution. It's that simple, and this applies to many areas of government interference including other industrial regulations, welfare, education, farming, etc.