This ESP32 comes with a battery holder at the back to provide power using a 18650 battery.
Scroll down to find the ESP32 at different stores and find the best price.
Aliexpress.com
Ebay.com
Shrsl.com
£11.90
1 new
from £11.90
1 used from £11.54
as of February 14, 2019 6:39 pm
$30.90
1 new
from $30.90
as of February 14, 2019 6:39 pm
Amazon.com