All of my convenience stores have it, but I do live in the quaint little bourgeois borough called Sanchong.
It’s probably harder to find in the working-class areas like Danshui.
You could also get Soda Stream and make as much as you want. They sell adapters that connects to a standard CO2 bottle so you don’t have to pay so much for their refills.
the mafia sure knows how to stretch that sh@#. but i guess the brand is more important than the actual source. same with olive oil, there’s far more (italian) olive oil on the shelves than there’s actually produced there. maybe putting on some sticker in italy on a bottle of finest recycled taiwanese motoroil makes it ok to go as extra virgin.