You can't make a gin and tonic without lime.
vape Train has a tonic flavor but BCF doesn't carry it. You can get it from Chef's in the UK or directly from VTA. Or, you could try the steeped INW Sparkling Wine idea.
I am working on one that I will share if it works out. FW has Tequila but I understand it is very weak, so FA Brandy might be a better booze option. Dave's (ID10-T) came up with a Margarita recipe that sounds good but I would change a couple of things about it. Dave is my favorite mixer and I base a lot of my recipes on his. The Piña Colada recipe was his and the changes I made were Dave approved.