Just duct tape a USB-C power bank to any modern ultra low power laptop. Especially ones with optional GPUs that don't have one installed. There's even software to treat them like the secondary batteries laptops used to have as an option.[0]
> Someone should make a laptop that's way heavier/thicker than current models but is also silent, cool, high-performing, and the battery lasts a week.
With a deep-travel backlit keyboard, FreeDOS, WordPerfect 5.1, DataEase 4.53, SuperCalc 5, and JPI TopSpeed Modula-2. (Oh, and Elite+, Prince of Persia, and the Infocom back catalogue for down-time).
[0] https://github.com/n4ru/FakeSlice