Here's a duplication of the concept used by the new Eclipse Morph bar. Multiple bar widths by disconnecting larks head, pulling bobbin out and threading through new hole and reconnecting larks head to the backline knot.
I used 2 aluminium kitchen draw handle, bent them a little more and drilled new holes. Used stainless self tapers through the bar part at and angle so less chance of pulling out. Used 6mm stainless wood screw through top of bar end.
Cost: around $20+
Cheers
Rich