Solar Panels can be used for either battery maintenance, or as a more significant charging source. A regulator is required if a certain ratio of panel size to battery capacity is exceeded. The safe limit is considered to be 10 watts of Solar Panel per 100Ah of battery capacity.
Here is a range of rigid and semi-flexible solar panels. Rigid panels are supplied mounted within aluminium frames. Semi-flexible panels are capable of being flexed in one axis, across a coachroof or deck.