I've bought a new Dahon Jack (26" wheel folder) frameset. I'm looking for a quick release stem, but something that will keep alignment. e.g. it comes with a collar that attaches to the steerer tube that the stem can attach and detach from. Does such a thing exist, or have I just made it up? I could have sworn I had seen one somewhere, but can't place it now. Anything else that would achieve the same result (remove / reattach bars without having to realign) is also welcome.