Boric acid is available at most department or drug stores, including Wal-Mart, or is available online at Amazon.com, as of 2015. It is available in a number of forms, including as an insecticide for roaches.
Since boric acid comes in forms for both medicinal use and use as an insecticide, it is important to purchase a product that is appropriate for the intended application. For instance, people sometimes use boric acid as an eye wash or for fungal infections, but the boric acid available for roaches may have other chemicals that are dangerous to humans. It is essential to read the ingredients carefully and dilute boric acid according to the package instructions when using it for medicinal purposes.