What do you mean by "natural", even vinegar is a chemical, it's an acid in very dilute form.
If you follow the directions given on a bottle of Jeyes fluid properly you have little to fear.
If you really want to go "natural" you can go outside with a bucket of dioxy-hydrogen and a scrubbing brush and remove it the old fashioned way. The moss will keep coming back eventually because of the location of the patio which encourages moss growth.