Here is what I did to mine to keep it from coming out while on the road. It is something like Wayne mentions. The strap had a plastic loop on one end and is looped around the metal bar at the top of the drawer and is attached to the front of the drawer with one of those metal attachments used to secure shades to RV windows and windshields. Cost about $1.50 at a flee market in Yuma. Hope the link isn't too long.
On edit: I'm having problems linking I'll try something else.
Lets try this one:
http://i35.tinypic.com/23msj9u.jpg