put a Schmidt. E6 halogen lamp on my new Bike Friday.. today,
I has their folding stem , a 1" quill in a 9/8 threaded fork
so had a mount for threaded headsets .. B&M , modified it to wedge on the
bottom part of the folding stem , it tapers a bit wider at the top, so a jammed fit at first .

will look for an O ring or so to make the grip better..

Need a wired taillight that will mount on a seat post,
as I have gotten to like my jump on and go lights .