I got the H4s from powerfuluk.com, listed as fitting various models including the range Rover P38.
However, they've changed the design now. Second set i got via ebay on a hunch and because they looked right. My hunch was correct. However from what i can see on ebay at the moment, most of the LED bulbs being sold aren't right.
As such i'd suggest :
https://www.classiccarleds.co.uk/col...nversion-9-32v
THey also have a freephone number, give Duncan a call there and have a chat with him see if he can make any other suggestions.