I've never had good results with a sun visor. Cycling cap works best for me. The short bill slants sharply downward and in the late afternoon you can adjust it to an angle that lets you see a lot of road without being blinded.

A helmet cover works very well in the cold, and probably rain if you get one that's water proof. I've never seen them come with the helmet. Mine cost about $20.00. I saw one priced at $40.00 +. It was Goretex, and I have no idea whether it worked or not. They completely missed the price point on that.