I do it old-school. I have a 20# CO2 tank, regulator, hosing, and appropriate valves. Maybe not old-school – what do you call that Victorian-era crap made modern? Anyway, it works, and I can make 2L of soda-water at a time. And serve beer from my kegerator.
Buy a soda stream carbonator from Amazon. Then buy the adaptor to allow use of the refillable tanks used for paintball guns.