2Pcs 18650 Battery Holder Li-ion Battery with Single Compartment, 18650 Battery Bank & Battery Backup, Support USB 5V/2A 3V/1A Battery Shield Charging Module with USB to MicroUSB Charging Cable

USB Power Bank / Boost Converter for ServosorA DIY power bank - they sell these circuit boards that hold 1, 2, or 4 18650 Lipo’s and have charging circuitry and regulated 5v and 3.3v outputs. Again you’ll need a boost converter to l provide higher voltage for the servo’s See https://a.co/d/08fDadss for the battery holder thing. It occurs to me you won’t need a boost converter if your servos are 5v or 3.3v - just feed the servo’s directly from the power source - not off the 5v/3.3v output on the arduino

Down with AAA batteries! A legacy nuisance, especially using 3 of them. I'd look for one that uses 18650 batteries personally. I haven't used this but maybe this would work: https://www.amazon.com/FORIOT-Battery-Compartment-Support-Charging/dp/B0CJR1Y967/ref=sr_1_10 Or maybe I'd keep looking until I found one that charged with USB-C instead of USB micro, but that kind of thing.