Accessories for LED lamps and methods of attaching accessories to illumination sources (e.g., LED lamps) are disclosed. A beam shaping accessories mechanically affixed to the LED lamp. The lens is designed to adapt to a first fixture that is mechanically attached to the lens. Accessories are designed to have a second fixture for mating to the first fixture such that the first fixture and the second fixture are configured to produce a retaining force between the first accessory and the lens. In some embodiments, the retaining force is a mechanical force that is accomplished by mechanical mating of mechanical fixtures. In other embodiments, the retaining force is a magnetic force and is accomplished by magnetic fixtures configured to have attracting magnetic forces. In some embodiments, the accessory is treated to modulate an emanated light pattern (e.g., a rectangular, or square, or oval, or circular or diffused emanated light pattern).