I'm certainly no expert but thought about a cover once myself. A looked around on the net, read this and that and most seem to like the ADCO brand.
I haven't bought one as found a place to store mine inside during the winter months.
2012 Fun Finder XT 276 Toy Hauler & Harley Davidson Ultra Classic with Condor wheel chock
2014 Dodge Ram 2500 AT 4X4 Crew Cab 6.4 L Hemi, 373 gears, tow package, Rambox option, Revolver X2 tonneau cover, Equal-I-zer anti-sway hitch.