Actually, for my grocery-getter to be (dad's beach cruiser, when I get it), I got one of the big Wald front baskets and fabricated up a hinged top to it, so that the bolts go through the mesh on the back, and hold on a wooden top that completely covers it. On the front then, I have attached two chains that have small key locks that attach to the front of the basket. It's not perfect, but it looks great (varnished wood on a red and white cruiser) and is definitely a deterrent. I plan on trying to fabricate something similar for the back, but will probably go with a bolted-on center board and hinges from there to the sides (a la picnic baskets). To prevent losses through the sides, I'm working on stitching up removable canvas liners for the rear pannier baskets. The front is mesh, so I'm not too concerned about that.