Polyend Play does not have an onboard battery but it runs on 5V 1A so any decent power brick will allow you to power it up.
Depending on the workload, a basic 20K mAh power brick will let Polyend Play go on for long hours or even days.
Important: The Simpler the power bank, the better. Please notice that an "intelligent" power brick with advanced power management systems or even a "smart" computer USB out used for powering can cause issues and turn Play unstable. The best method to power up your Play unit is to use the original AC adapter.