Amazon has the APC Back-UPS Connect BGE90M [amazon.com]
for $24.99. Shipping is free with Prime or orders of $25 or more (1 cent below free shipping
"The BGE90 UPS backup battery helps you stay connected to the Internet during power outages
Ultra efficient small UPS design maximizes runtime for low-power devices such as Amazon Echo and network routers
4.5 hours of extended runtime provides instant battery power to your critical electronics when the power goes out
3 outlets provide battery backup power and surge protection with convenient USB ports to recharge mobile devices, including tablets, during an outage"