On that note, I think i've found my lens. I've got an old pair of binoculars that never get used laying around, so I unscrewed one of the front lenses, went outside in the dark, and I was able to get an in-focus image of the moon on the focusing screen of my rb67 just by holding the lens in front of the camera body. Its pretty small, looks like 35-45mm in diameter, but there's no noticeable vignetting on the focusing screen even at infinity, so the size of the image circle seems not to be a problem. All I need at this point is a crappy rb67 lens. Lets hope KEH has some nice ugly lenses.