There is another website that may be able to host one time purchases.
Nutaku is a western h-game publishing company,
that also runs a website that hosts games that they themselves
did not publish.
The thing is, the company Nutaku sees themselves like steam, however, they are more like the google playstore, a lot of the popular games on that website are free gacha games with ai generated art, however it isn't too uncommen for normal h-games to be sold on the website.
Since the website only offers 18+ games and is pretty much only present in the western market. They will have to fight payment processors in court should they try to force them to ban 18+ content
Atleast that is what i know about them