I've got one of these:
http://www.bicycleclothing.com/Water...et-Covers.html

It works quite well. If you read my reply to your other posting,a jacket with hood will alliviate the need for a cover.

As for combining a cover/hood with a head light;best thing I could say would be to MacGuyver some kind of mount off the front of your helmet,or just get a headband flashlight. PrincetonTech makes a 1W LS headlamp that's waterproof and would prolly work over the top of the cover/hood.