It’s not easy being a ruler. Do you know how much stuff you need just on a daily basis? Vials of poison, lots of sharp pointy things, and probably a few music boxes with “The Rains of Castamere” at the ready. The job of ruler is taxing, so you better make sure you’re able to carry everything you need to get the job done. Or if you can’t get the job done, at least make sure the people that are heckling you never speak again. Either one works in this scenario.
Messenger bag sporting Lannister pride for all your royal needs. Hold all your riches in all the extra pocket space, including a sleeve for your otherworldly electronic laptop.