My solution would be to order a package of Sugru, make an eyecup yourself, and use the rest of it to make a grip for the camera, or fix things around the house. I'm quite enthusiastic about the stuff, by the way, and propose it as a solution for pretty much anything :tongue:
Mind you, whether it looks anywhere near as polished as the OEM part depends very much on your level of handiness and the amount of thought you put into it...