Are you sure its not just the background LEDs that have failed? The reason I ask is that it is more common for the climate control screen to fail as it is used each time you start the car ie the time etc. I have located a site in the USA that can supply the climate control screen RHD for LS400 and Sc400 up to 1994 as these are the screens that, as I said, usually go first. The price is around $90 US plus postage.
Cheers
Ric