Chair leg spring? (Rawtenstall BB4)

Hi, has anyone got an old chair that has these adjustable feet on that's no longer fit for use?
I'm looking for the spring that goes in them (or the whole foot section/chair).

The spring is a barrel spring (wider in the middle) that's 1mm thick steel, 30mm long and goes from 5mm diameter at the ends to about 8mm.

Thank you,
Matty