Sash Ribbons (Tapes?)

Once again, our house is special.  I guess I knew that already, but here's another reminder.

The topic of "Never before seen sash 'ribbon'" came up on The Historic District recently.  The person posting the question had only seen double-hung windows balanced with cord or chain, never a metal ribbon or tape.

Double hung windows need some mechanism to keep them open.  There are a number of different ways to accomplish this, including some sort of counterbalance mechanism.  Typically a sash cord runs over a pulley near the top of the window opening.  One end of the cord is attached to an appropriately sized weight and the other is attached to the sash.  The sash end is usually knotted to that the knot fits into a mortise in the edge of the sash and doesn't come loose.  Sometimes, sash chain is used rather than cord.

Occasionally, you'll see a "tape balance".  Rather than a pulley, a spring-loaded cartridge is mortised into the jamb near the top of the window.  The cartridge and spring will be sized for the weight of the window and play out the proper amount of metal ribbon.

Our windows use a normal counter-weight and pulley system, but use a metal ribbon instead of cord or chain.  Apparently, this is rare.

The first photo shows a broken ribbon from a couple of years ago when I was restoring the Music Room.  Note that the face of the pulley between the flanges is flat; evidence that it was meant for ribbon rather than cord or chain.

The next photo shows how the ribbon is attached to the weight inside the weight pocket.  It's turned back on itself to make a loop for the weight hook.

The last photo shows how the ribbon is attached to the edge of the sash.  It's turned back on itself around the buckle which is then pressed into the mortise so it doesn't come loose.  There's a small nail whose head also helps keep the buckle in the mortise.

The sash ribbons in the kitchen are steel; a magnet will stick to them.  I haven't tested the material on the other windows, though.  The ones in the latter two photos don't look like steel to me.  Doing some internet searching, apparently the ribbons were made out of one of two materials: steel or aluminum-bronze.

Over the period we've been in the house I've tried to find a source for the ribbon, but have so far struck out.  If you have any suggestions, please let me know.