Try white tea. It is the youngest phase of tea leaves. It has the highest antioxidant content of all teas, and, just for you, the lowest caffeine content. I could not drink it because I can only drink black tea - the rest, including green, is, unfortunately, not palatable to me. You can get plain or flavored white tea. If there is trader joes in your area, you can buy white tea with pomegranate and return it if you do not like it. They probably carry plain white tea as well. If you have trader joes, I would start there since they gladly accept returns.

African plant called Roibos (unsure of spelling) produces tasty "tea" that is very high in antioxidant content without any caffeine whatsoever. Again, trader joes has it.