G'day RMB,
It looks like that part has gone obsolete, as I can't find any online parts supplier who lists it. A faint hope would be that it was superseded by a later part number - the ODK Shop should be able to advise on that.
I guess at least you have part of the original spring, which will give you the wire diameter to use if you try making one up - 'music wire' is the stuff to use. It's available in ~1m lengths, from hobby suppliers; e.g. this mob seem to stock a good range of diameters -
https://www.smallparts.com.au/store/partslist/wiresteelspringmusicwireshortlengths/ And the IPL does show the general shape of the spring quite well.
A Google for 'making springs from music wire' finds a lot of how-to info and vids.
