The only thing I can suggest would be careful masking and painting. I am not sure what kind of paint would work. There is Fabric paint out there but some sort of generic spray paint might be a better option. I am guessing that material is plastic. I would find something similar(...an old duffel perhaps) and try some paint to see how it responds.
Careful masking and spray paint should look pretty professional when its done if you prep it right.
Theres always that rubberized coating in a can.
Oh, make sure whatever paint you get will hold up to the heat you put it through. Most paints are not up to the heat inside a car during the summer and can bubble.