I have an old Surefire 628 on my mp5, and would like to place an IR filter on the light for use under my pvs14- but for the life of me I cannot find the appropriate Surefire fm43 or z63 window. I did find an FM45 (red) filter so really all I need is the Z63 IR window, though I would be willing to buy the whole FM43 assembly if someone has one available.