I have a J & G rain cape
http://www.bicycleclothing.com/Rain-Capes.html
The inside waist tie and sewn in elastic thumb loops are essential, but even then I find I need to scrunch up a good couple of inches of fabric to keep it taught across the handlebars otherwise it flops down and all the water drains off in front and soaks you underneath, and in a heavy downpour water comes in around your neck so you still get soaking wet. A veltop like the one’s shown above might be better, or a crap Chinese knock off like this might work but you’ll be thrown about in the wind if you put the sides down
(Link Removed - No Longer Exists)