I'd hit the RISC OS web page and mailing list but no, in decades of shows and more, never saw such a thing. Probably due to low sales or only a few folk in the world asking.
Does this laptop, notebook, ultrabook, whatever device, exist? Are they currently manufactured? Or am I going to have to make it myself?
17 Inch ARM Quad Core Numeric Keypad Removable Battery.
"Numeric Keypad" means a device with long internal keyboard includes numeric keypad.
"Removable Battery " means to set to Hibernate or even Shut Down, two latches to remove the battery easily, and insert a spare battery, and then power on again. AND also ability to switch batteries while plugged in. The device must function with no battery installed.
I am not bothered by the manufacturer nor the cost of this device.
Supports RISC OS.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic