kettledrum I had acquired one that hadn't been used from my deceased friend - was never used, son gave it to me and I could not get gas bottles for it, so sister bought me a new one. You just can't get the old bottles well as far as I am aware.
Wolf 63 - get yourself one - you mix the water until it is fizzy then add your favourite juice.
Argos Soda Stream. And you can also get your replacement gas bottles in Argos as well when you run out.
When I partied mine was used a lot to make sparkling water as a good few of my guests took sparkling water in their drinks so it was great then. Just treat yourself. They are not too expensive - around £40.