I would send an email to North Hollywood Speedometer.
http://www.nhspeedometer.com/ They can probably repair it for less then a replacement. They do so much custom stuff that replicating unusual stock features would be nothing.
Also there must be VDO repair shops on your side of the pond. I would guess that one of them could do the same type of work. I would even ask NHS if there was a shop in England they could recommend.