I don't think that foam between the screen and keyboard will help - it's blows and buffets to the back of the screen - i.e. the lid - that cause the damage.
I'd go for a rigid backpack model like the Samsonite Sugo Business Laptop Backpack. Your criteria may well be different, so search for "laptop hard cases" for a good idea of what's out there, and what the prices are like.
SD