You know the little clamp-on pulley wheel that holds the cable at the top of the seat tube on an English three speed bike? Well, I need on of those, but a double one. Two pulley wheels, side by side on the same axis. An item so rare and bizarre that if you have one, you may not even know what it is.
For this rarity I'll trade you... oh, I dunno, what do you need? I'm sure I have it, though.