is there a slipcase for 17" MacBook Pros which opens at the side? I carry my 17" MBP in my laptop pannier, into which it just fits in portrait orientation.  I'd like to protect it with a slipcase, but I don't want to have to take the slipcase out of the pannier to get at the laptop.  Is there a slipcase on the market that opens at the side?
I've certainly seen them around the place, I've got a portrait one myself. 

How about this?