Back when men were men and bikes only had 10 gears I used to commute to work in a pretty heavy duty rubberized rain poncho. It looked like an olive drab 4 X 8 tarp with a hole in the middle for a hood. I remember draping the front of the poncho over my handlebars which actually my legs relatively dry. That's relatively dry - not real dry or even fairly dry. I think that I bought it at a place that sold budget priced work clothes.