Hi Gordon,
I assume these are the ones you mean, see below; they're more like 50 mm unstretched. They look a bit strange (like double helix) in the picture due to shadow. I have a couple I can donate to the cause; send me your address and I can mail them.
I don't think you'd find these for sale. More likely found from scavenging W110/W111 handles which use the same parts.
Meyer