It’s a rather small (yet utterly lucrative market) – from what I recall there are 2 suppliers – Fox – at around £55 per unit for the standard one that comes with the forks or a German company (Tune perhaps) – at around £150 (from what I’ve heard) for a unit but it is very light.
I had mine stretch and had to buy a new one…the new design (from mid-2010 (I think)) are a better design as mine didn’t stretch but some internal piece failed…the new design doens’t have this and is less likely to fail like that.
But over £50 for that wee piece…it’s a right royal rip-off but needs must.