This company manufactures bike covers for a living
Waterproof Motorhome bicycle cover from Oxford Products. This Bicycle cover is capable of covering 1 or 2 bikes.
It has a compartment to contain the commonly used warning signals. The product is lightweight, waterproof and comes with a 300D silver coating. Very easy to install and complete with integrated bungee fittings.
A good high quality product that fits onto the rear of the rack for Thule, Fiamma and others