Thanks for that link Cat! I've not dealt with Flashlightlens.com myself, but others over at BudgetLightForum have. I've even heard that the owner will custom make sizes for you (at least for certain lens types). I might have to try a couple of these. I do see though that they have a warning about not being very scratch resistant.
patski - no, I've never seen that, nor have I ever heard of using the colored LEDs for night vision.