So much for Armytek’s 10 year warranty :person_facepalming: This is repairable if you have some basic tools. The main issue is getting the bezel off, because this style has thread locker. There is an excellent guide on how to remove it here:
After that you just need a replacement lens from one of the usual sources. From what I recall, most Armyteks this size us a 20mm x 1mm lens, which is $2.25 at Kaidomain. You should double check the size with calipers before ordering through.
http://kaidomain.com/S022290-20mm-D-x-1mm-T-Multi-Layer-AR-Coated-Lens-1-pc