One of the ways I had contemplated protecting my saddle and seat post on my folder from being stolen was to make my own cable. That is, to select a rubber coated length of cable, cut it to the full extended length of the seatpost, and then swage the ends (no lock - permanent). I have a friend that makes side-stay rigging for sail boats and he can easy swage the fittings for me. I'd use a lightweight cable because if someone has bolt/cable cutters it won't matter the thickness. This would keep the casual stealer/passerby from taking the parts.