There are several different options. One is the lens kit directly from Malkoff Devices. Another option is to go to flashlightlens.com and get the Borofloat 22.61mm x 1.10mm lens or .95mm thick AR coated lens in 22.61mm diameter. A sapphire crystal with AR coating option is the 22.5mm x 1mm offering from The Sandwich Shoppe.