The Asahi Bellows Unit S is a tiny, foldable bellows for M42 thread mount cameras and lenses. Provides more than 2x magnification with 55mm or 58mm lenses, according to the on-rail scales; should do similar work with other lenses of similar focal length. Smooth geared adjustment, good locks. There is a tripod socket at the camera end, but it's pretty minimalist, so you may want to stick with smaller lenses. But, again, this thing is tiny when it's folded up, so the tradeoff is likely worth it.