Mike - I have a Renogy panel, and it performs well. I think that you can wind up paying a lot for portable solar, especially the kind that roll up. I recall that someone posted they got 60W for $600. That is way too expensive.
Is this the type of panel you are looking for? It is rigid, but folds up and does not have a controller.
https://www.renogy.c...w-o-controller/
One important thing to note is that the polarity of the wiring from the Zamp plug will be reversed from the wiring from other manufactures. In other words, the positive wire on the Renogy panel will connect to the negative plug on the Zamp port. Further, if you get a Renogy (or likely other manufacturer), you'll need an adaptor to for the wires on the panel. A simple fix would be to snip the connector wire and simply switch the wires so that the positive wire plugs into the positive port.
Not having a Zamp panel will introduce a few more steps. Check out this post.
http://www.wanderthe...olar-connector/
So, here is a summary...
Find portable solar panel without controller
Determine what connector is needed to attach panel to Zamp plug
Check polarity and change if needed