There is a great post on the Land Rovers Only Forum that has compiled a great collection of the part numbers for the Air Idler Valve. The part is very pricey if you source if from the major Land Rover online sites like Atlantic British and Rovers North. Those are the two I use, there are others as well.
The part is a common GM part for Chevy Astro vans and S-10 pickups. You can read the post to get all the part numbers and then you can source the part from your favorite provider.
It’s basically a reprinting of the great stuff found on Rangerovers.net at this link with even more part numbers.
Finding parts for 20-year-old Range Rovers is getting harder and harder every day. Have you looked for a fan resistor kit lately? There are none to be had presently.
Thanks for reading and Happy Rovering.