Charging a baby monitor issue/question

This one is a little out of my wheelhouse, but I have an Infant Optics baby monitor (base unit and 2 cameras) that we use for our daughters. While the monitor usually lasts a majority of the day, longer naps means less charge and it can be dead halfway through the day. I have it hooked up to a PoweCore Speed 20000 for when we still are using it and want to move around the house with it, but it does not seem to want to push a charge to it, only keeps it from dying. Same goes for just charging it with a PowerPort II, shows charging and as soon as you remove it, it shows significantly less charge. Stock Samsung fast charge block yields the same result. I took a look at the power brick that came with it and it is only a 550mH, which using that with any cable works fine. Question is am I screwed into only using the PC speed as a “keep alive” and only getting a full charge from the stock wall block, or is there a power bank that pushes out only 550 mA?