In order to power your chordata we recommend using a regular cellphone Powerbank.
It should be rated for at least 2A. To have a durable supply a capacity of at least 10000mAh is desirable.
Even if technically powerbanks are not designed to power a system like this, we like them because they are ubiquitous and inexpensive. And they can also be used on other jobs like, of course, recharging your phone 😛
But, this leave us with a chance that a particular powerbank won't work with Chordata. It never happened to us, but it's possible. So the question is: Which powerbank are you using? can you post the brand, specs and perhaps a picture here?
That way other users can get a trustable reference of what to buy.