Are you specifically looking for battery operated? Because you could just get a smart outlet and attach them to it if they were wired.
I've yet to see any battery operated yard lights that are worth buying - heck, I've yet to see one that lasts more than a year.
I'm confused what you are not finding. There are so so many smart switches on the market, they dim, and then the dim all the way to off.
They don't have a relay, they just (more or less) dim until the light is off.