Has to be said, I'm not all that surprised that you didn't come across it, ince it's not one of those things that you'll find being served in bars - you'll find it in shops, though. I think that the creeping march of Coca-Cola capitalism probably means that its days are numbered in any case.
One of the major sources when I was young(er) was "The Maine Man" who delivered fizzy pop door-to-door on trucks - just like the milk man but without the health benefits.
Whether such mobile providers of fizz still exist is a mystery to me. The fact that they ever existed is a chronic reflection on the diets we had back then.