I've been in a similar position. The secret is to be underneath the rain cover yourself. I would start with a large trash bag, a rubber band, and a lens hood if you have one. Cut a small hole in the bag for the lens, put the lens (with the hood on) through the hole, and rubber band the bag around the outside of the hood. The hood will keep rain off the lens element, and give the rubber band something to squeeze other than the lens. Finally, you can fit your head and shoulders underneath the bag. You will now be able to see through the lens without any trouble, and you'll stay dry-ish too!