I upgraded from a very obvious laptop sleeve on strap to
http://www.pacsafe.com/intasafe-z500-anti-theft-backpack.htm...Steel wires through the straps, and looks like a backpack. I'm also big enough that unless it is rip and run, or a clear and unambiguous threat to my life, I'm not as concerned, so having a strap which won't break is enough.
