Try the forsale sections of all the x5 forums mate, this is normally a good place to start as most other owners would rather sell "in house" than on ebay etc, and most times for cheaper money.

$800 - $1k should get you both 16:9 screen and a mk4, less for a mk3.

Remember to get the screen for an x5 (NOT the e39 and 7 series) these display units are no good as they have the wrong rake on the display for the x5.

If you were in the UK I could help out with a mk3 or a mk4 as I have one of each spare, but alas you are across the pond.

__________________
Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.