You could use technology currently available today.
Ingredients: 1 Oxygen, 2 Hydrogen, 1 fuel cell.
A fuel cell converts the chemicals hydrogen and oxygen into water, and in the process it produces electricity.
If I'm not mistaken, these fit the bill. https://www.buygreen.com/products/pem-reversible-fuel-cell?utm_medium=cpc&utm_source=googlepla&variant=3181636609&gclid=Cj0KEQiAzsvEBRDEluzk96e4rqABEiQAezEOoBJRRj_6y4mYPozErvoaD8Rwit9BQfOSoieG959rFN0aAs5X8P8HAQ
However you'll have to call the company to confirm and/or test them out before relying on them for the gas giant.
Unfortunately I don't have the reputation to comment on my own answer (nor is there enough room) in response to: "Note that using electrolysis to make the fuel cells takes more electricity than the electricity it will produce. – Anketam", so I'm responding here.
Anketam, thanks for your comment. First, note that electrolysis is not used to make fuel cells. Electrolysis of water produces hydrogen, which I presume is what you're actually referring to. Converting that hydrogen back to water may or may not produce less electricity than went into producing the hydrogen, but it does make sense as there are likely to be losses in the system. On the other hand, perhaps the scientists in the OP's world have perfected the system to 100% efficiency.
Second, note that the OP is seeking a source of water not a source of electricity. The electricity is simply a byproduct of producing the water. It's a bonus. Yes, it costs electricity to make water. Perhaps electricity is free on the OP's world.
Third, note that solar panels can be added to the system to generate electricity (and hydrogen/oxygen gases) during the day, and the hydrogen can be used at night and during cloudy periods to generate electricity and water.
In this configuration hydrogen functions as a battery in a sense. Obviously there are other ways to generate electricity as well such as wind for example so electricity is essentially "free" - after the initial capital investment of course and any ongoing maintenance which should be minimal. Perhaps volunteers donated their time to building the system and therefore cost nothing but their donated labor. Or not, as the OP chooses for his world.