I found mine at a hardware store
Most hardware stores will have at least a small selection of these locks with various lengths. If you can't find one locally, check out some of the woodworking sites on line; like Rockler, which has one for 3/4" stock for about $12 (part #98998).
I modified mine so it fits flush with the surface (Ya; I know, its a little anal) so I can't give you a part number that would necessarily fit yours.