Battery Operated Starry String Light 100 LED (Included Rechargeable 18650 Battery) with Automatic Timer 8 Mode Copper Wire String Light for Christmas Outdoor Holiday Decorations (Warm White) selling for $5.66
I have seen plenty of 3AA battery versions, but this one uses a 18650, which is included.
As far as I could find out, a full charge takes you for around a week if you have the timer proper.
The box is the charger, that seems easy to plug/unplug to charge with a usb adapter.
I liked the idea here, seems to me all the good stuff come together on this one and the price seemed not too bad either.