I think finding solar + controllable by HA is going to be tough to find unless your roll your own or modify an off-the-shelf unit with an ESP32 connected to a battery and larger solar panel. Does it need to be solar? You could use the WLED board and some outdoor pixel lights and have some seriously cool outdoor lighting if you can wrangle up 5V of power for it.
Currently I do not have 120v in the backyard so I was hoping for some solar powered string lights.
It might be a little more complex than I thought it would be.