Meee, I also use Soda Stream. The carbonator is about $100. Target, Bed Bath and Beyond carry it. It comes with a replaceable compressed air bottle. The bottle lasts me, I live by myself, for about a month. I go to BBB and get a replacement bottle, $15.
I use it for carbonated water. Healthy, and after the initial purchase, the compressed air bottles are excellent value for what I pay for it.
The carbonator does not need electricity. It is light weight and I keep it in the kitchen shelf and pull it out as I need it.