Nothing prevents you from doing your own solar setup like that. There are plenty of external solar panels/batteries. Having said that, if you’re talking about an always-on camera/continuous recording, the specs you’re talking about would require a pretty bulky setup. For your reference, the panel on top of this guy’s mailbox powers a V2 camera for about 2.5 days. That means you’d need to triple the size of that panel if you want a week of backup power. You also need the battery, which would probably be brick-sized or so.
If you’re talking about a panel to power a camera that only records when motion is detected by a PIR sensor, that could potentially make more sense to build into a camera itself.