My thinking on solar charges: if it sits in the sun then it gets hot, batteries don't need the heat, so maybe a panel that sets in the sun and a separate charger that connects but can sit in the shade. Many of the small chargers I looked into have such low voltage it would take days to charge batteries. C. Crane Company lists a charge for D to AAA that claims 150mAh and 5 volts, an old Brunton model I have only does 140 at the 6v setting, it could trickle charge a cell phone just didn't do much for batteries

A search of Folding Solar panels should give some choices, many with chargers for AA and AAA built in. Since I wanted a panel for a lot of reasons I chose a large rollable panel that should pack enough power to rapid charge batteries. I'm still trying to decide on the charger but I have been looking at these chargers
or these chargers
I'm looking for a rapid charger "smart" enough not to fry the batteries