There are a lot of useful comments here.
If someone can recommend good-quality solar panels (preferably those that roll up) ... that would be useful.

The SIMPLE thing I got from this discussion ... don't try to charge your phone directly from the solar panel. This takes too long. Instead, buy a couple of rechargeable batteries. Leave the solar panel so that it is constantly charging one battery for the entire day (e.g. leave on the roof of your vehicle or cabin). Carry the other battery(fully charged) as a backup. And this way there is always an opportunity to re-charge your phone if you need to.

THANKS. excellent suggestions!!
Pete