OK, sorry - I apologise - I missed that specific post (slap wrist !)
So, understanding that you aren't able to 'make' your own, how about 'mixing' your own
Using carbonated water as a base (Tesco, ASDA all stock it very cheaply) how about adding some Lemon Juice for a no-sugar lemonade. If you like ginger beer you can buy - bit difficult to find admittedly - Ginger Syrup (try a specialist cooking / chefs suppliers)
Other alternatives could be lime juice, lemon & lime together or maybe one of the nice cordials by 'Bottle Green', a weak Elderflower spritzer would go well with some of the 'peatier' single Malts