Go to http://www.randpcarriages.com and click on parts and it will take you to their ebay page. You will find some oval tail light enclosure boxes. Not sure how sturdy they are, but maybe the only thing missing for icy landings are the cages over the lenses like Jon Jordan said.
I have these boxes after having my new LED lights broken in a parking lot. These are very heavy duty. Not sure if it is legal to put a cage over the lamp.