I make my own. The intial expense is a hit, but after that it is real cheap to make.
It's important to make it correctly, but it isn't hard. Don't believe that it has to be strong to do the job.
What I make ranges from 6ppm to 10 ppm. Don't believe all the BS some of these people that sell it try to tell you about the strength.
It's also excellent if you feel a cold, sore throat, or flu coming on. Have a dropper bottle on hand and a 2 oz spray bottle. Forget Flu shots, and cold remedies. Gargle for the throat, a couple of drops on the ears and nose will keep them away.