Jackery, Rockpals, etc...
The DIY Solar Power with Will Prowse channel has good reviews on batteries and solar panels:
YouTube

you should expect to pay about $1/Wh or less

I have a group 31 AGM and 100W solar panel on the 4Runner but still have a small Rockpals (300W 280Wh) for portability around the campsite and to run an apap

(Note for @85GT-79FJ40 if you get something for your cpap, make sure it doesn't turn off automatically. The Jackery will turn off the 12V DC port after a certain amount of hours if you aren't pulling enough watts, and most cpaps are below that watt limit so don't get the Jackery. The Rockpals doesn't do this, and can even be used in UPS mode which will just pass through power from 120V but automatically switch to battery if you lose power, good feature for cpaps if you live somewhere that loses power from storms or something. For camping run your cpap on DC, it uses a lot less power that way)