Thanks! For the larger coil that goes around the rear of the scope/barrel mount I used an old audio component coiled cord:
The smaller coiled cord that connects to the right-hand greeblie plate is still in work actually. I have one that came with my bag of greeblies and it has the right cord and coil diameters (smaller than the rear coil) but this one is a bit too short and 'plasticy stiff' for my taste so I've got a couple of eBay vintage cords coming soon and I'll update here when I find something that works.
Markus et al. are probably good resources for what the actual vintage cords were on the screen-used prop...