The upper fan shroud for a 97 4.0L V8 is the same part and part number as used on similar 4.0L Discos. There are a few threads on this on here for a part number, including a few I added to assist your search and I've seen them on Ebay, etc. for good prices.
It's the lower D90-specific fan shroud part that's difficult/impossible to find, and when ordered through dealers it's pretty much always replaced in the package with the similar Disco part. The difference is that using the lower Disco one requires it to be trimmed to fit the different mounting for D90 engine ancillaries, etc. A long time ago I laid my 97 D90's one on top of a Disco one for comparison, and confirmed it was the case as reported elsewhere.
'97 D90SW - SOLD SEP '14
'94 D90ST - SOLD MAY '13
D90s sold while assigned overseas. You're welcome America!
'06 Range Rover Sport Supercharged
'8X FankenRover D100