This is probably not exactly what you’re looking for, but I rode across the USA (4200 miles across 12 weeks) about a decade ago and this is what I did:

I used an ancient kindle to display my pdf route/cue sheet from a clear pouch on a handlebar bag that I could easily read and “flip through” while riding. (You can also just use paper) The battery life lasted long enough to get through every week of campsites where power isn’t promised. We’d stop at a hotel about once a week just to have a nice shower and charge our things. Of course I also had a full set of maps as well, but they are more difficult to read while you’re riding- thus route/cue sheet.

I had my phone and would use GPS if I feel like I got lost. I didn’t have great service in large patches of the route, but the gps works regardless, so as long as you have the GPX files, it should point you in the right direction.

I also have a SON hub dynamo that lead to a Sinewave Cycles Revolution USB charger (there’s probably more modern USB chargers you can buy nowadays). But with that I charged a usb power bank and was able to charge my phone every night.

I’d also be interested if there exists a singular device like that that is able to last a long time on a tour. Good luck and have fun on the road!!