There's a couple places that sell rainsocks....Here's a drag specialties one.
http://www.dragspecialties.com/fatbook/12/73/5906931

I run mine open, and have been caught in some really bad downpours with no real issues except the already stated oil getting on the side of the bike & increased cleaning required.

 

Golf.....I have a stage 2 BS. Get a pair of spandex shorts or pants, Cut the leg to the needed length. Put the hemmed side behind the rubber gasket and the cut side behind the cover. I was able to run a lighter on the cut line to avoid fraying. I had a pair of high quality (black) riding shorts from my dirt riding days. Because of the elasticity of the shorts they fit the filter perfectly. And you being a woman I bet you have a dozen or more options in different colors.


Edited in. PS: I have no problems in the rain.