As an American I had to do a lot of research to figure out what sort of "lemonade" would work best for this drink, since the "lemonade" called for is specifically the carbonated UK variety. Lemon-lime soda seemed like it would be far too sweet and insufficiently lemony, so I tried Sanpellegrino Limonata. The drink was far too sour and the mint tasted very odd underneath all the citrus. Any suggestions for something commonly available in the US?