Painting rubber knives

Anybody have a favorite type of paint or other way of getting black rubber training knives to look metallic? I often just spraypaint them, but that cracks and peels with use. I've tried metal foil tape stuff, but that also gets wrinkled on one side and stretched out on the other when the blades bend.

Either of these can still work, they just require regular touch-ups, which can be a pain.