Frankly guys, this is a bit of a luxury! It serves no function other than putting the light on, and if you can't tell when the choke needs pushing back in then there's something much more serious wrong!
There was one of these on Ebay the other day, but I've just had a look and I reckon it's finished. Otherwise try Rover Classics, Wadhams etc.
For those of you new to the car, Ebay is a pretty standard way of getting new components for the P6 and it's amazing what obscure bits come up. Check it out!
Chris