I just picked up one of these little guys:
it attaches to the car with magnets and keeps all kinds of crap out of the charging port when you've got the cable attached. This morning there was 3cm of snow on the car, but the port (and charger) was clear and dry. It's a bit awkward, but like anything else you kinda get used to using it.
Let me know if there is interest and I'll share the link to the website.