Atlas Shrugged Posted: This is a solution looking for a problem. I tour regularly and use a Garmin 1040 Solar which in battery saver mode is good for 100 hours in moderate battery save mode. That is 12 days of riding 8 hours a day with no access to outside power which would be a very particular use case. The longest I have every been off grid has been 7 days and my battery pack tides me over just fine until I hit a charging point.
The 1040 is $650.00 to $750.00. The Phone I posted is $250.00. I would need to carry a phone and a GPS cycling computer. I like the available phone mapping and apps for bicycle travel better also.