If the laptop will be powered on then you need a power bank with an inverter of equivalent wattage as listed on the GL503's power brick. (180W I believe?)
If you will only use it when powered down it will draw less but that's not a published stat. Someone would need to use a watt meter when it's half drained, charging, and powered off.
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…