http://www.menards.com/main/electrical/alternative-energy/solar/18-watt-solar-charger-kit-with-7-amp-charge-controller/p-1509038-c-7916.htm18 watts for $100 is expensive per watt and will not do more than maintain one or two fully charged and disconnected batteries.
Honestly I think you are far better off with 100 watts minimum to make the effort.
80 watts $104Better controller $42OK that is a few $$ more but it will actually do something while camping.
DM Solar 85 cents per watt (316w) Need larger controller too.
Get something that works or just pass for now. Maybe a second battery for now.