Or try this: a few years back I got a warrantied remaindered solar panel at: Solar Electric Inc. in San Diego http://www.solarelectricinc.com/
. They have some really good deals on all sorts of factory-second photo-voltaic (PV) panels. I got one of the Unisolar 32 watt (2A at 16V) flexible panels.
The cool thing about this type of panel is that it is unbreakable, you can roll it into a pretty small radius and store it away. You can mount them on any flat or curved surface. Move them around, walk on them, whatever. And then roll them up and store them away when you're done.
The Unisolar panels (including their rigid panels) have a series of internal diodes that allow the panel to keep producing current, even when partially shaded. They do have a lesser rated output for their size than some other panels, but they do work in partial shade and so will produce more energy than some other rigid solar panels in real-world situations. And of course, the flexible panels are a bit more expensive, but not outrageously so.
You can also put it away from your trailer if necessary (I attached an extra-long cord) to get maximum sun. With a permamently-mounted panel, you've kind of resigned yourself to parking in the sun...