Leica parts no longer sells the rubber coated eyepiece used on the M6, M7 and MP, fortunately, Don Goldberg has a snap on plastic cover. They work well, stay on and don't cost a lot. Recently, there is a seller on E-bay with a similar product for the M cameras. I'm trying one now to compare to the DAG cover. The problem is with a camera like the Retina where there isn't a ready made product. I've tried the stick on felt but inevitably they fall off at the most inappropriate time. Rubber O rings are a great idea but finding an adhesive that will both keep the ring in place and not out gas into the finder is a problem. I looked at silicone caulk, leather washers, nylon washers and any number of other gimcracks. The attraction to the Retina is it fits in a jacket pocket. Most of the stick on eyepiece covers is they come off in the pocket. Hopefully, this will stay on. Thanks for all of the suggestions.