Computer centers are great for putting together bomb-proof covers for the 505! I bought two, each made of slightly different material, and put one inside the other. Both are clamshell zipped, but I cut off one end so I could top-load the reader without having to remove the case from my bag, cutting through the zipper, then gluing over the remaining zipper to keep it from opening. The outer bag is made from a fairly stiff foam giving lots of protection from impact. The inner bag is made from 5mm neoprene giving great protection from shock and vibration. Together they are just slightly larger than the 505 in its original cover, providing very secure carrying in all conditions while still allowing me to just reach in and slip out the book for a quick page or two. For more security I can slip in hard plastic panels between the two bags if needed for activities such as Brahma Bull riding, Moto-Cross, or Demolition Derby, but these don't come up very often.
Stitchawl