backpacks made especially for cameras are usually padded and have velcro dividers that you can place so your camera is held snuggly.... take a look at them.... they may not fit what you need now, but are worth checking out.
check out a LowePro... sounds like what you want.... lightly padded. zippered closure, usually a small pocket for extra batteries or flashcards...... you can get one that fits your camera perfectly or get a longer one so you have the option of putting a longer lens on.... with a longer bag your camera won't jostle around because there are velcro dividers that support the body
http://www.lowepro.com/Products/Toploading/
http://www.lowepro.com/Products/Topl...der_65_AW.aspx
http://www.lowepro.com/Products/Topl...der_70_AW.aspx
http://www.lowepro.com/Products/Topl...d_Zoom_AW.aspx
http://www.lowepro.com/Products/Backpacks/