How do I find every health food store in America?

It is unlikely anyone has had success compiling a list of 90% of the
Health food stores in the USA. The last 10% would be very costly and
involve deciding if a store that carried 9 health food items and 9000
other items should be listed as a health food store? How about a
Shackly dealer who works out of her home and has $1000 in gross sales
for the decade?  Neil

By the way; many South Americans consider themselves Americans, so you
should say USA if you don't want to include Guatamalla and Bolivia.  
Neil