This is something my husband came up with as the solution to our refrigerator opening up and spilling it's contents while we are towing. Works great and didn't cost a thing.
We have a two door refrigerator which has the reversing door option. So, it has a hinge between the two doors with a hole in it in case we want to have the doors open the other way. We use this hinge as the base for our refrigerator lock. We just pull a long twist tie through the hole in the hinge and then wrap the twist tie around a small block of wood that holds both doors in place. See attached examples.
We never have a mess to clean up anymore and the solution was a no cost item. Being Yankees we love that part.