I found this for you! http://www.seltzersisters.com/index.html
home delivery for seltzer water in the San Francisco bay area!
You could also try Safeway, they do home delivery now
when I was doing research to answer this question, I did find make it at home seltzer water, but I wanted to focus on the delivery. I’m glad you found a solution, and one that will save you money versus delivery!