How about these from Flying Spares www.flyingspares.com here in the UK. The listing says
1001- SUBFRAME DAMPER (BENTLEY CARS) UR73254 £99.09
Don't know if they are the same for the Spur. You could phone them I suppose.
However, how about something like this on www.ebay.co.uk . I'm sure you may have something similar on Ebay.com. Look up item number 140134378235 (UK Ebay). It may just suffice and its a damn site cheaper. Maybe you could email the guy to get some proper dimensions, but it certainly looks to be in the right ball park.
I'll take a look at them. I have bought from Flying Spares before. The problem with buying from the UK is that shipping to the US usually costs enough to to knock out any savings from purchasing locally.
"I've never seen a substitute for sale at a lower cost and there should be. The Rolls-Royce dealers are selling "aftermarket" dampers for high prices. These dampers are such a simple thing, keep looking, somewhere we should be able to buy "aftermarket ones for realistic prices.....we need to find out the company who is making the "aftermarket" dampers.....