Oddly enough I found the best alcohol alternatives whilst we were in.....Australia!
As others have said, lime and lemon with a splash of Angustura bitters (actually available as pre-mixed in bottles and cans over there) or, to me, the best is Bundeberg Ginger Beer. Absolutely nothing like the Idris stuff you get here, this is proper stuff, refreshing and doesn't burn your tongue or throat. Bundeberg is available over here, if you know where to look (I tend to buy it by the case from Costco)
Good luck FF, keep it up.