I had a bit of success today.
Going through boxes/bags/containers of bits looking for something unrelated, I found some springs. Seven of them. I have no idea how or why I have them.
The springs to be replaced, as best as I can measure, are 0.3mm wire thickness, 12mm long by 2.56mm diameter.
The ones I have found are slightly smaller, 0.3mm wire thickness, 10.75mm long by 2.35mm diameter.
They might work. I'll give them a go.
The question now is, why did I have them?